Chapter 2 Tissues Short Answer Type Question And Answers

Question 1. If a potted plant is covered with a glass jar, water vapours appear on the wall of glass jar. Explain why?
Answer.

If a potted plant is covered with a glass jar, water vapours appear on the wall of the glass jar

It occurs due to transpiration.

 

Question 2. Discuss the characteristics of meristematic tissue.
Answer.

The characteristics of meristematic tissue:

The cells are oval, rounded or polygonal in shape. The cells are living with thin cellulose walls and without any intercellular spaces The cells are rich in cytoplasm with very small vacuoles. The cells are diploid and undergoes mitosis. The cells do not contain reserve food materials, endoplasmic reticulum and plastids.

Question 3. Discuss the characteristics differences between sclerenchymatous fibres and sclereids.
Answer.

The characteristics differences between sclerenchymatous fibres and sclereids:

Question 4. What are sieve tubes?
Answer.

Sieve tubes:

These are slender, tube-like structures that consist of elongated thin-walled cells, placed end to end. The end walls of these cells are perforated by several pores and are known as sieve plates.

Question 5. Describe the differences between tendons and ligaments.
Answer.

The differences between tendons and ligaments:

Question 6. Discuss the differences between bone and cartilage.
Answer.

The differences between bone and cartilage:

Question 7. What are phagocytes?
Answer.

Phagocytes:

These are capable of phagocytosis and helps in the defence of body by engulfing bacteria and other foreign substances. Phagocytes are of two types, namely granulocytes and agranular leukocytes

Question 8. Discuss the differences between endocrine and exocrine glands.
Answer.

The differences between endocrine and exocrine glands:

Question 9. Describe characteristic features between unicellular and multicellular glands.
Answer.

Characteristic features between unicellular and multicellular glands:

Question 10. Discuss the differences between plant and animal tissues.
Answer:

The differences between plant and animal tissues:

Question 11. What do you understand by the term ‘Division of labour’ in the organisms?
Answer:

‘Division of labour’ in the organisms:

Division of labor in organisms enables a smooth and efficient functioning in the body for better survival. Different functions are performed by different groups of cells in an organism, and this is called division of labour in the organisms.

Question 12. What is histology?
Answer:

Histology:

The study of tissues is known as histology.

Question 13. What do you understand by tissue?
Answer:

Tissue:

Tissue is a group of cells that are similar in structure and organized together to perform a specific function.

Question 14. Where is apical meristem found?
Answer:

Apical Meristem:

Apical meristem is present at the growing tips of stems and roots. Their main function is to initiate growth in new cells of seedlings, at the tip of roots and shoots.

Question 15. Discuss the characteristics of plant tissues.
Answer:

The characteristics of plant tissues:

• Plant tissues provide mechanical strength to the internal as well as external organs.
• Provide elasticity and flexibility to the plant organs.
• Plant tissues help in the transportation of materials across the plant body and prevents loss of water.
• They undergo division to help the plants to grow both in length and girth.
• The plant tissues are involved in many metabolic processes, such as photosynthesis, respiration, etc.

Question 16. What are meristematic tissues?
Answer:

Meristematic Tissues:

Meristematic tissue is a group of dividing cells that has the capacity to divide and re-divide and help in the growth of plants.

Question 17. What do you understand by the term histogen?
Answer:

Histogen:

Dermatogen produces epidermis, where periblem gives rise to cortex and endodermis and plerome to vascular bundle and pith. These three layers were termed as histogen.

Question 18. Discuss different types of meristematic tissues.
Answer:

Different types of meristematic tissues:

Question 19. Discuss the characteristics features between meristematic and permanent tissue.
Answer:

The characteristics features between meristematic and permanent tissue:

Question 20. How are simple tissues different from complex tissues in plants?
Answer:

Simple tissues are made up of one type of cells which coordinate to perform a common function. Complex tissues are made up of more than one type of cells. All these coordinate to perform a common function.

Question 21. How many types of elements together make up the xylem tissue? Name them.
Answer:

Xylem is a complex tissue. It is made up of the following four kinds of cells or elements.

• Tracheids
• Vessels
• Xylem parenchyma
• Xylem fibres

Question 22. Which tissue makes up the husk of coconut?
Answer:

The husk of a coconut is made up of sclerenchyma tissue.

Question 23. What are the constituents of phloem?
Answer:

Constituents Of Phloem:

Phloem is the food conducting tissue in plants. It is made up of four components as listed below.

• Sieve tubes
• Companion cells
• Phloem parenchyma
• Phloem fibres

Question 24. Discuss the differences between parenchyma, collenchyma and sclerenchyma.
Answer:

The differences between parenchyma, collenchyma and sclerenchyma:

Question 25. Discuss the characteristics features between xylem and phloem.
Answer:

The characteristics features between xylem and phloem:

Question 26. What do you understand by stomata?
Answer:

Stomata:

Stomata are the pores found in the epidermis of leaves, stems and other organs, which are used to monitor gaseous exchange.

Biology Chapter 1 The Fundamental Unit Of Life

If you ever come across a brick wall being constructed, then you can see that bricks are the basic building blocks of a wall. Similarly, cells are the fundamental units of your body. In simple definition, cells are sacs of fluid enveloped by membranes with chemicals and organelles embedded inside the fluid.

Though an organism possesses few other structures that are smaller than a cell and yet, however, cell is considered to be the smallest part of an organism. Robert Hooke (1665) discovered the cell, while studying a thin slice of cork through a crude microscope. He observed that cork resembled the structure of a honeycomb having many small compartments.

He called these little compartments as ‘cells’ (in Latin, ‘cellula’, which means ‘a little room’). His discovery was published in a book ‘Micrographia’. The ability to produce energy, synthesize hormones, transmit hereditary factors are examples of a few events that take place within the tiny building blocks of life called ‘Cells’.

Read and Learn More: NEET Foundation Notes

Chapter 1 The Fundamental Unit Of Life Architecture of Living Organisms

When you observe the inner layer of an onion by dropping iodine solution followed by a cover slip under high powers of a compound microscope. The structures of inner layer look similar to each other. Together they form a big structure like an onion bulb. Hence, we concluded that any organism despite different sizes have similar small structures visible under microscope.

The small structure that we observe are the basic structural and functional unit of onion bulbs. There are also single cells that live on their own, such as Amoeba, Chlamydomonas, Paramecium, and Bacteria. These organisms are called unicellular organisms. Many cells group together in a single body to form multicellular organisms like fungi.

Invention of the Microscope

Invention of the microscope was a milestone with regard to learning the delicate details of internal arrangement of the cell. Cells are microscopic structures not visible to human eyes. Anton van Leeuwenhoek is the father of microbiology who in the late 17th century became the first man to make and use a real microscope.

Ordinary compound microscope is an optical instrument that consists of two convex lenses of short focal lengths. This microscope can magnify the image of a tiny object up to 1000 times. Electron microscope uses electron beams to illuminate a specimen object and create a magnified image.

It magnifies to over 2,00,000 times the magnification of an ordinary compound microscope. The variations between the working of a light microscope and electron microscope is discussed.

Differences between light microscope and electron microscope

Cell Theory

Jacob Matthias Schleiden (1838), a German botanist and Theodor Schwann (1839), a German zoologist stated that cells are the fundamental and building blocks of all plants and animals. Their discoveries led to the formulation of the cell theory. They postulated that all animals and plants are made up of cell.

History of cell biology

Rudolf Virchow (1855) further refined the cell theory and gave the idea that all cells arise from pre-existing cells.

The main postulates of the modern cell theory are as follows.

• All organisms are made up of one or more cells and cell products.
• All metabolic reactions occur in cells. Hence, cells are the structural and functional units of life.
• All cells arise from pre-existing cells, as an animal gives birth only to an animal and a plant gives rise only to a plant.
• An organism begins its life as a single cell.
• Virus is an exception of this theory.

Chapter 1 The Fundamental Unit Of Life Cell Shape

Living cell has the capacity to perform certain basic functions that are characteristics of all living forms. Depending upon the functions perfomed by cells are of different shapes and sizes. Most plant and animal cells are basically the same when formed.

By the processes of maturation and differentiation, they acquire different forms. Different parts in human body performs different functions. The human body has heart to pump blood and stomach to digest food.

Eukaryotes are organisms with a well-defined membrane bound nucleus and other organelles. Eukaryotic cell is spherical in shape, but ultimately the shape of a cell is governed by the specific function of the cell. The shape of the cell may be variable or fixed.

For example, amoeba changes its shape and white blood cells or leucocytes are spherical in circulating blood, but in other situations they become irregular in shape by producing pseudopodia. Cells have fixed shape in most of the plants and animals.

In unicellular organisms, the cell shape is determined by the hard plasma membrane (for example, Paramecium) and exoskeleton (for example, Elphidium). In multicellular organisms, the cell shape is mainly determined by its functional adaptations, and also by the surface tension, viscosity of the protoplasm, the mechanical pressure exerted by adjacent cells and the presence of a rigid cell wall such as in plant cells.

Cell Volume

Cell volume is almost consistent for a specific cell type and it is not dependent on the size of an organism. For example, in a bull, horse and mouse, the kidney and liver cells are almost of the same size. The variation in the total mass of the organ as well as organism is determined by the number and not the volume of the cells.

Cell Number

The number of cells in organisms is related to the size of the organism. Hence, the small-sized organisms have less number of cells as compared to the largesized organism. In most multicellular organisms, the number of cells is not fixed, except a few such as rotifers and nematodes. In human beings, the number of cells present in the body is approximately 100 trillion (10¹⁴).

Chapter 1 The Fundamental Unit Of Life Master Your Test Question And Answers

Question 1. Who discovered cells and how?
Answer: Cell was discovered by Robert Hooke in 1665 while studying a thin slice of cork through a crude microscope. He observed that cork resembled the structure of a honeycomb having many small compartments. These compartments were later known as cells.

Question 2. Why cell is called the structural and functional unit of life?
Answer: Cells are called the structural and functional unit of life because all living organisms are made up of cells. These cells carried out specific functions which is important for life processes.

Question 3. Write the main postulates of cell theory. Who propounded the cell theory?
Answer: Rudolf Virchow propounded the concept of cell theory and gave the idea that all cells arise from pre-existing cells. The main postulates of the modern cell theory are as follows.

• All organisms are made up of one or more cells and cell products.
• All metabolic reactions occur in cells. Hence, cells are structural and functional units of life.
• All cells arise from pre-existing cells, as an animal gives birth only to an animal and a plant gives rise only to a plant.
• An organism begins its life as a single cell.

Question 4. Differentiate between prokaryotic and eukaryotic cells.
Answer:

Chapter 1 The Fundamental Unit Of Life Structural Organization of a Cell

Microscopic studies reveal that most cells have the same basic structural architecture. The cells have a jellylike substance called protoplasm bound by a cell membrane. The term protoplasm was coined by Purkinje in 1839. The protoplasm consists of the cytoplasm and a spherical body called nucleus. All the cells possess the following three major functional zones.

• The cell membrane or plasma membrane and the cell wall
• The nucleus
• The cytoplasm

Plasma Membrane

The plasma membrane is the outer boundary of the cell, enveloping the cytoplasm. In the cytoplasm, all the cell organelles and inclusions are embedded. All the cell organelles like mitochondria, chloroplasts, lysosomes, peroxisomes, Golgi apparatus, nucleus and endoplasmic reticulum are enclosed by the unit membrane. In animal cells, the plasma membrane is present in the outermost layer of the cell, whereas in plant cell it is present just beneath the cell wall.

Structure

Plasma membrane is a thin (about 7 nm), delicate, elastic, and selectively permeable membrane. The membrane is almost made up of 75% phospholipids. Also, it consists of proteins, cholesterol and polysaccharides.

Fluid Mosaic Model: S. J. Singer and G. L. Nicolson (1972) proposed a model called the fluid mosaic model to explain the structure of functional cell membranes or plasma membranes. According to this model, the plasma membrane is made up of a double layer of phospholipids.

The plasma membrane allows the movement of only certain substances across it and prevents the rest. Hence, it is selectively permeable. Two kinds of protein molecules float in the fluid phospholipid bilayerand they are explained as follows.

• Intrinsic or integral proteins completely cover the lipid bilayer.
• Extrinsic or peripheral proteins occur either on the outer surface or on the inner surface of the lipid membrane.

Functions

• Plasma membrane is a selectively permeable membrane, which regulates the entry and exit of the cell contents.
• It performs some physical activities, like diffusion and osmosis for the intake of some substances.
• In addition, some other biological activities like active transport and endocytosis are performed by the plasma membrane.
• The fluid nature of the plasma membrane makes it flexible and enables it to engulf substances or remove wastes by vesicle formation.
• Certain factors present in the plasma membranes play an important role in cell recognition in immune receptors.

Transport of Substances Across the Plasma Membrane

The passage of substances across the cell membrane takes place by three models listed as follows.

• Passive transport
• Active transport
• Bulk transport

Passive Transport

1. Diffusion: Certain substances can easily pass through the plasma membrane by a simple process of diffusion. Diffusion can take place in all states of matter and however, it takes place faster in the gaseous state.

Diffusion is the net movement of solute particles from a region of high concentration to the region of low concentration. When there is a difference of CO₂ concentration, inside and outside of a cell, gas moves out of the cell to the external environment, i.e., from the region of its higher concentration to the region of its lower concentration with the help of diffusion process.

Similarly, oxygen (O₂) enters the cell by the process of diffusion when the concentration of O₂ inside the cell becomes lower such as in Amoeba.

Diffusion is significant to biological systems due to the following reasons.

• Helps in the uniform distribution of substances in the cytoplasm.
• Assists in exchange of gases which is critical to processes, such as respiration and photosynthesis.
• Helps in attracting insects for pollination by spreading the scented chemicals from flowers.
• Helps in diffusion and the nutrient chemicals get absorbed into cells in the intestine of digestive system.

2. Osmosis: Osmosis is the passage of water or solvent from a region of high solvent concentration through a semi-permeable membrane to a region of low solvent concentration. Osmotic pressure is the external pressure needed to be applied so that there is no net movement of solvent across the membrane. Osmosis was first observed by Jean-Antoine Nollet (1748).

Osmosis is a mechanical diffusion process through which cells absorb water without spending any amount of energy. Osmosis is significant to biological systems due to the following reasons:

• Helps in the absorption of water by the roots from the soil.
• Helps in closing and opening of stomata on the leaves.
• Assists in cell-to-cell movement of water.

While studying the effects of different solutions on plant and animal cells, three conditions may arise depending upon the tonicity of the solution.

Hypotonic solution: When the medium surrounding the cell has a higher concentration of water (a very dilute solution) as compared to the inside of the cell, the cell will gain water by osmosis. This dilute solution is called hypotonic solution. In this situation, the cell swells up, as more water will enter the cell than leave the cell. These swollen RBC’s may finally burst, i.e., haemolysed.

1. Isotonic solution: When the medium surrounding the cell is of precisely the same water concentration as the cell, there will be no net movement of water across the membrane. This solution is called isotonic solution. For example, Ringer’s solution is an isotonic solution for the animal cells. In this condition, water moves across the plasma membrane in both directions and the amount of water going in is equal to the amount going out. Hence, the cell will retain the same size.

2. Hypertonic solution: When the medium has a lower concentration of water (a very concentrated solution) than the inside of the cell, the cell will lose water by osmosis. This concentrated solution is called hypertonic solution (Fig. 1.7). Here, water moves across the plasma membrane in both directions, but more water leaves the cell than enters the cell. Hence, the cell will shrink. In this condition, the plant cell gets plasmolysed and the animal cell gets crenated.

3. Facilitated transport/diffusion: The permease helps a molecule to diffuse through the membrane that it cannot penetrate alone. It promotes movement in a downhill direction only, i.e., in the direction of the concentration gradient and needs no metabolic energy to carry out the transport system. For example, in many animals, the facilitated diffusion helps in the transport of glucose (blood sugar) into the body cells that oxidizes it to get ATP’s.

As the amount of glucose is more in the blood than in the cells that consume it, an inward diffusion takes place. Because glucose is a water-soluble molecule that on its own cannot penetrate the membrane rapidly enough to support the metabolism of various cells, the mediated transport accelerates the inward flow of glucose.

Active Transport

The energy is provided to the system (‘pump’) to transport molecules in a direction opposite to a concentration gradient. It promotes movement in uphill direction, i.e., against the forces of passive diffusion. This involves expenditure of energy from ATP as substances are pumped against the concentration gradient.

The best example of active transport system in all animals is the maintenance of sodium and potassium gradients between cells and the surrounding extracellular fluid. Most of the animal cells need a high internal concentration of potassium ions for protein synthesis by the ribosomes and for some enzymatic activities.

The concentration of potassium ions is about 20–50 times more inside the cell as compared to the outside of the cell. On the other hand, sodium ion concentration is about 10 times more outside the cell as compared to the inside of the cell. Active transport maintains both these ionic gradients by transporting potassium ions into and the cell sodium ions out of the cell.

Bulk Transport

Bulk transport involves the movement of macro-nutrients, such as proteins, polysaccharides which can pass only through ruptured plasma membrane. Large molecules generally cross the membrane in bulk by endocytosis and exocytosis.

1. Endocytosis: The process by which material moves into the cell. It is of three types, namely phagocytosis(cell eating), potocytosis (cell drinking) and receptor-mediated endocytosis. All the three processes require energy.

• Phagocytosis: It is the process by which a cell called phagocyte takes in or engulfs or eats other cells or particles. The newly-formed phagosome then fuses with a lysosome whose hydrolytic enzymes digest the ’food’ inside. For example, white blood cells (leucocytes) that engulfs cellular debris and unwanted microbes in the blood. Other phagocytes are also present such as the macrophages found in connective tissue and liver sinusoids.

• Pinocytosis: The cell engulfs drops of fluid by pinching in and forming vesicles. Similarly to phagocytosis, pinocytosis is an unspecific process where the cell takes in any of the solutes that are dissolved in the liquid it encloses.
• Receptor-mediated endocytosis: It is a very selective process of importing substances into the cell. In this process, the receptor proteins present on depressed areas of the cell membrane (‘coated pits’) determines this specificity. Coat proteins cover the cytosolic surface of coated pits. The cell will only pick up an extracellular molecule when it binds to its specific receptor protein on the surface of the cell. When binding is done, the coated pit on which the bound receptor protein is situated then pinches in, to produce a coated vesicle. This coated vesicle now fuses with a lysosome to digest the engulfed substance and release it into the cytosol.

2. Exocytosis (Cell vomiting): Exocytosis is the process by which the intracellular vesicles in the cytoplasm fuse with the plasma membrane and release their contents into the surrounding medium.

Exocytosis takes place in many cells for the following purposes.

• Removes undigested material brought inside the cell by phagocytosis.
• Secrete substances like hormones, enzymes, etc.
• Transport a material wholly across a cellular barrier, for example, an immunoglobulin (IgA) or antibody is picked up on one side of the blood vessel wall by phagocytosis, transported across the cell and released by exocytosis.

Summary of movement methods across membranes

Chapter 1 The Fundamental Unit Of Life Cell Wall

Cell wall is a rigid, non-living and freely permeable layer that lies outside the plasma membrane in plant cells. It protects the cell and its contents and determines the shape of the cell, and prevents desiccation of cells. It consists of a fibrous polysaccharide (carbohydrate) called cellulose.

Thus, the cell wall consists of minute cellulose fibres called microfibrils, which are cemented together by a mixture of polysaccharides. Each microfibril consists of numerous cellulose molecules bound together by pectins and hemicellulose.

Structure of Plant Cell Wall

Basically, the plant cell well consists of three layers and it is briefly explained as follows.

• Primary cell wall: A thin, flexible and extensible layer formed when the cell is growing. It provides the strength and flexibility required to allow the growth of cells.

• Secondary cell wall: A thick layer is formed inside the primary cell wall when the cell is fully grown. This layer is not found in all types of cells. Only some cells, such as the conducting cells in xylem have secondary wall consisting lignin that strengthens and protects the wall from water.
• Middle lamella: An outermost layer rich in pectins forms the interface between adjacent plant cells and cements them together.

Functions of a Cell Wall

• Cell wall makes the plant cell turgid. When water enters the vacuole through osmosis, the plant cell expands. The cell wall provides strength to the cell by providing turgidity to resist this expansion.
• Cell wall provides mechanical strength to the cell with the help of cellulose microfibrils. In xylem, lignin is present to provide additional strength. In collenchyma cells, extra amount of cellulose is present in the cell wall which increases the mechanical support.
• Cell wall is freely permeable to solvent and materials in solution.
• Cell wall consists of narrow pores known as pits through which very fine strands of cytoplasm known as plasmodesmata are able to pass. These intercellular connections permit the exchange of substances between the living cell contents.
• Middle lamella is a pectin layer that cements the cell walls of two adjoining cells together, which gives stability to the plants and also permits the plants to form plasmodesmata between cells. This layer is made up of calcium and magnesium pectates. This is the first layer that is formed and deposited during cytokinesis.

Plasmolysis

The phenomenon in which a living plant cell loses water through osmosis leading to shrinkage or contraction of the protoplasm away from the cell wall is called plasmolysis.

Chapter 1 The Fundamental Unit Of Life Track Your Learning Questions and Answers

Question 1. A science student was viewing a rose plant cell through an electron microscope, where the student observes the presence of a hard rigid wall and a very thin delicate wall in the cell enclosing the cytoplasm.

How can we call that thin delicate wall?

1. Cell wall
2. Middle lamella
3. Plasma membrane
4. Nuclear membrane

Answer. 3. Plasma membrane

Question 2. Gaseous exchange in amoeba takes place through

1. Osmosis
2. Photosynthesis
3. Diffusion
4. Exosmosis

Answer. 3. Diffusion

Question 3. In ______, permease assists a molecule to diffuse through the membrane that it cannot penetrate alone.

1. Facilitated transport or diffusion
2. Active diffusion
3. Osmosis
4. Pinocytosis

Answer. 1. Facilitated transport or diffusion

Question 4. Name the ‘energy currency of the cell’.

1. GTP
2. ATP
3. DTP
4. ADP

Answer. 2. ATP

Question 5. Phagocytosis is

1. Cell eating
2. Cell drinking
3. Cell death
4. Cell vomiting

Answer. 1. Cell eating

Question 6. Pinocytosis is

1. Cell eating
2. Cell drinking
3. Cell death
4. Cell vomiting

Answer. 2. Cell drinking

Question 7. Exocytosis is

1. Cell eating
2. Cell drinking
3. Cell death
4. Cell vomiting

Answer. 4. Cell vomiting

Question 8. The cell wall consists of minute cellulose fibres called

1. Microfibrils
2. Microsomes
3. Microtubules
4. Microns

Answer. 1. Microfibrils

Chapter 1 The Fundamental Unit Of Life Nucleus (‘Brain of the Cell’)

The nucleus is membrane-bounded, centrally-located, spherical structure present in the eukaryotic cell. There are two nuclear membranes forming a nuclear envelope. There is a space between two nuclear membranes, which is connected to a system of membranes known as endoplasmic reticulum (ER).

The nuclear envelope makes the nucleus distinct from the cytoplasm. It also contains many pores called nuclear poresand it consists of the liquid ground substance called nucleoplasm. Nuclear pores permit the transfer of substances between the nucleoplasm and the cytoplasm.

The nucleoplasm consists of the nucleolus and chromatin material. The nucleolus is not bounded by any membrane and it is rich in protein and RNA (ribonucleic acid), and thus, it acts as a site for ribosome production. Ribosomes help in protein synthesis in the cytoplasm.

The chromatin is a thin, thread-like entangled mass of chromosome material and it consists of the genetic material DNA and proteins (i.e., histones). The chromatin is formed of repeating subunits called nucleosomes. Each nucleosome has a DNA molecule coiled around a disc of histones.

DNA is considered to be the blueprint of life as it contains all the required information for the cell to function, to grow and to reproduce. Genes are the discrete segments of DNA. During cell division, the chromatin material gets condensed into two or more thick ribbon-like chromosomes.

Functions of Nucleus

• Nucleus controls all metabolic activity of the cell.
• Nucleus regulates the cell cycle.
• Nucleus controls the transmission of hereditary characteristics from the parent to offspring.

Chapter 1 The Fundamental Unit Of Life Master Your Test Question And Answers

Question 1. What is chromatin?
Answer: The chromatin is a thin, thread-like entangled mass of chromosome material and it consists of the genetic material DNA and proteins (i.e., histones). The chromatin is formed of repeating subunits called nucleosomes.

Question 2. What is plasmodesmata?
Answer: Cell wall consists of narrow pores known as pits through which very fine strands of cytoplasm known as plasmodesmata.

Question 3. Which organelle is known as the powerhouse of the cell and why?
Answer: Mitochondria is known as the powerhouse of cells because the energy required for various chemical activities needed to support life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.

Question 4. Where do the lipids and proteins constituting the cell membrane gets synthesized?
Answer: Lipids are synthesized in smooth endoplasmic reticulum and the proteins are synthesized in endoplasmic reticulum.

Question 5. What are nuclear pores?
Answer: The nuclear envelope makes the nucleus distinct from cytoplasm. It also contains many pores called nuclear pores and it consists of the liquid ground substance called nucleoplasm.

Question 6. What are the functions of nucleus?
Answer:

• Nucleus controls all metabolic activity of the cell.
• Nucleus regulates the cell cycle.
• Nucleus controls the transmission of hereditary characteristics from the parent to offspring.

Chapter 1 The Fundamental Unit Of Life Track Your Learning Questions and Answers

Question 1. Name the ’protein factories of a cell’.

1. Peroxisomes
2. Lysosomes
3. Ribosomes
4. Nucleus

Answer. 3. Ribosomes

Question 2. Genes are the discrete segments of

1. RNA
2. ATP
3. mRNA
4. DNA

Answer. 4. DNA

Question 3. ______ provides a specific shape to the chromosomes owing to its position.

1. Centromere
2. Centriole
3. Peroxisome
4. Oxysome

Answer. 1. Centromere

Question 4. Human beings have ______ pairs of chromosomes.

1. 21
2. 22
3. 23
4. 46

Answer. 3. 23

Question 5. Diffusion is fastest in

1. Solid phase
2. Liquid phase
3. Semi-solid phase
4. Gaseous phase

Answer. 4. Gaseous phase

Question 6. What will happen when a cell is kept in an isotonic solution?

1. Shape of the cell changes.
2. Size of the cell remains the same.
3. Will shrink
4. Will swell

Answer. 2. Size of the cell remains the same.

Question 7. The process of withdrawal of water from a cell through osmosis is called

1. Endosmosis
2. Exosmosis
3. Both (a) and (b)
4. None of these

Answer. 2. Exosmosis

Question 8. When exosmosis occurs in a plant cell, it is

1. Plasmolysed
2. Re-plasmolysed
3. Non-plasmolysed
4. None of these

Answer. 1. Plasmolysed

Question 9. Transport of substances across the plasmalemma against the concentration gradient is

1. Active transport
2. Passive transport
3. Bulk transport
4. All of these

Answer. 1. Active transport

Question 10. Unicellular freshwater animals and most plant cells tend to gain water through the process of

1. Diffusion
2. Osmosis
3. Imbibition
4. Facilitated diffusion

Answer. 3. Imbibition

Question 11. Fluid mosaic model of the plasma membrane was given by

1. Schleiden and Schwann
2. Singer and Nicolson
3. Knoll and Ruska
4. Huxley

Answer. 2. Singer and Nicolson

Question 12. The phenomenon by which protoplast of a cell shrinks from the wall is called

1. Osmosis
2. Plasmolysis
3. Diffusion
4. Glycolysis

Answer. 2. Plasmolysis

Chapter 1 The Fundamental Unit Of Life Cytoplasm

Cytoplasm is the region of the cell located between the plasma membrane and nuclear envelope. Cytoplasm is a living, colourless, semi-liquid and homogenous substance. It occupies a major part of the cell and it is constantly moving.

Cytoplasm consists of a watery ground substance, called the cytosol, which contains the various cell organelles as well as other inclusions like insoluble wastes and storage products (glycogen, starch, etc.). Cell organelles are found embedded in the cytosol, and each of these has specific and important roles to play.

Cytosol forms the ground substance of the cytoplasm, in which all the cell organelles are embedded. It contains a system of protein fibres known as cytoskeleton. Cytosol is almost 90 per cent of water, which contains all the molecules and ions needed to support life. Cytosol serves as a store of vital chemicals, like amino acids, glucose, vitamins, ions, etc.

Endoplasmic Reticulum (ER)

ER is a membranous network enclosing a fluid-filled lumen that almost fills up the intracellular cavity. ER is connected to the outer membrane of the nucleus at one end, whereas the other end is connected to the plasma membrane. ER occurs in the form of three parts, namely cisternae (closed, fluid-filled sacs), vesicles and tubules.

There are two types of ER and they are explained as follows.

Rough endoplasmic reticulum (RER): Ribosomes are attached on its surface for protein synthesis.

Smooth endoplasmic reticulum (SER): No ribosomes are attached and it helps in secreting lipids.

Functions of ER

• ER acts as a supporting skeletal framework for the cell.
• ER helps in the passage of nuclear material between the adjoining cells.
• RER helps in the synthesis of proteins by ribosomes on their surface.
• In vertebrates, SER of liver helps in detoxification of various toxic or poisonous substances that enter the animal’s body through food, air or water.
• SER is involved in the biosynthesis of glycolipids, phospholipids and cholesterol.
• SER is involved in the synthesis of steroid hormones, like estrogen, testosterone and cortisol.
• RER produces hydrolytic enzymes of lysosomes. From RER, the hydrolytic enzymes are transported to Golgi apparatus where it gets included into lysosome.
• ER helps in the formation of plasma membrane and other cellular membranes. SER produces lipid molecules for cell membrane and gets inserted into SER membrane. RER is involved in the synthesis of protein molecules of cell membrane. In the process of glycosylation, small chains of sugars known as oligosaccharides are added to molecules of proteins and lipids at the level of Golgi apparatus.

Ribosomes

Ribosomes are dense, spherical and granular particles that are present freely in the cytosol or it remains studded to the RER. Ribosomes mainly consist of the ribonucleic acid (RNA) and proteins. Ribosomes are not bounded by membranes.

Function of Ribosomes

• Ribosomes play a crucial role in the synthesis of proteins.
• These are considered to be the factories of protein in a cell. Actually, one ribosome cannot perform protein synthesis.
• In 1963, Gric and Hall published the detailed role of polyribosome in protein synthesis and showed that active units are no individual ribosome, instead a group of these units are known as polyribosomes.

Types of Ribosomes

Basically, there are two types of ribosomes, such as 70S and 80S ribosomes. Here, S denotes Svedberg unit, which is the sedimentation coefficient that depicts how fast cell organelle sediments in an ultracentrifuge. Sedimentation coefficients cannot be additive.

80S ribosomes occur in eukaryotes, such as algae, fungi, higher plants and animals. In animals, the 80S ribosome is made up of a large 60S subunit and a small 40S subunit.

70S ribosomes are comparatively smaller and occur in prokaryotes such as bacteria. The 70S ribosomes are made up of a large 50S subunit and a small 30S subunit.

Interestingly, ribosomes found in mitochondria and chloroplasts of eukaryotes resemble to the ribosomes of prokaryotes and not to the 80S eukaryotic ribosomes.

Golgi Apparatus

Golgi apparatus is an arrangement of membrane-bounded, fluid-filled vesicles, vacuoles and flattened cisternae (closed sacs). Golgi apparatus originates from the membrane of the SER that in turn has originated from RER.

The proximal Golgi saccules (cisterna at cis face) are produced by fusion of ER-derived vesicles, whereas distal saccules (cisternae at trans face) are fully used for vesicle formation and vanish. Hence, Golgi saccules are renewed constantly and speedily.

Generally, the cisternae are stacked together in parallel. There are two faces of Golgi apparatus, such as Cis face of Golgi, where cisternae are formed and trans face of Golgi, where vesicles are budded off.

Functions

• Golgi apparatus acts as an assembly area for the storage, processing and packaging of various cellular secretions.
• It is involved in the synthesis of cell wall, plasma membrane and lysosomes.

Lysosomes

Lysosomes are small, spherical, single membrane-bound, sac-like structures uniformly distributed in the cytoplasm and it consists of digestive enzymes. These lysosomal enzymes are produced by RER.

Functions

• Lysosomes act as intracellular digestive system by destroying any foreign material that enters the cell and hence, these are called digestive bags. By doing this, they protect the cells from any harmful effect of foreign material such as from bacterial infection.
• Lysosomes remove the worn out cellular organelles by digesting them so that new replacements are done. By doing this, they remove the cell debris. Thus, lysosomes act as a type of garbage disposal system of the cell. These are also known as demolition squads, scavengers and cellular housekeepers.

• At the time of breakdown of cell structure, lysosomes may burst and the enzymes released eat up their own cells. Thus, lysosomes are also known as suicidal bags of a cell.

Mitochondria

The mitochondria are small bodies of varying shapes and size distributed in the cytoplasm. Each mitochondrion is enclosed in a double-membrane envelope. Outer membrane is having pores, whereas the inner membrane is thrown into folds called cristae, which are studded with tiny rounded bodies called F1 particles or oxysomes.

The internal cavity of the mitochondria is filled with a proteinaceous gel-like matrix that contains some smallsized ribosomes, a circular DNA molecule and phosphate granules.

Functions

• Mitochondria serve as the sites for cellular respiration. They utilize molecular oxygen from air to oxidize the carbohydrates and fats present in the cell to carbon dioxide and water vapour. Energy is released during oxidation and some part of this energy is used to form ATP (adenosine triphosphate). As mitochondria synthesizes energy-rich compounds hence they are called ’power house’ of the cell.
• Mitochondria can synthesize some of their own proteins, and DNA, due to which they are also considered as semi-autonomous organelles.

Plastids

Plastids are present in most of the plant cells, but absent in animal cells. The plastids have their own DNA and ribosomes and so they are self-replicating organelles similar to mitochondria. Plastids are mainly of three types and they are listed below.

• Chromoplasts: Coloured plastids (excluding green colour)
• Chloroplasts: Green-coloured plastids
• Leucoplasts: Colourless plastids

Functions

• Chloroplasts help in photosynthesis in which they manufacture food for the plant by trapping solar energy. These are called ‘kitchens of the cells’.
• Chromoplasts impart various colours to flowers and some leaves that helps in attracting the insects for pollination.
• Leucoplasts stores food in the form of starch, fats and protein.

Chloroplasts

Chloroplasts consist of a green pigment called chlorophyll, which helps in photosynthesis. Each chloroplast is enveloped by two unit membranes (Fig. 1.23). The two separate regions shown in the chloroplast are as follows.

• Grana are stacks of membrane-bounded, flattened discoid sacs (known as thylakoids) consisting of the chlorophyll molecules. These are the main functional units of chloroplasts. This is the site of light reaction during photosynthesis.
• Stroma is the homogeneous matrix in which grana are embedded. Stroma consists of various photosynthetic enzymes, starch grains, DNA and ribosomes. This is the site of dark reaction during photosynthesis.

Vacuoles

Vacuoles are fluid-filled or solid-filled; usually single membrane-bounded spaces. In animal cells, the vacuoles are rare, small and temporary. They store water, glycogen and proteins. Vacuoles serve as osmoregulatory organelles in protozoans and ingestion of nutrient material in amoeba and paramecium.

In plant cells, the vacuoles are large, distinct and permanent. In mature plant cells, the vacuole occupies almost 90 per cent volume of the cell and takes a central position. Due to this, the nucleus and other cell organelles are pushed near the cell wall. The vacuole is bounded by a membrane known as tonoplast and filled with a water solution called the cell sap.

Functions

• Vacuoles maintain the osmotic pressure in a cell.
• Vacuoles store toxic metabolic by-products or end products of plant cells.
• Vacuoles give turgidity and rigidity to the plant cells.

Peroxisomes

Peroxisomes are minute, single membrane-bounded, spherical organelles consisting of powerful oxidative enzymes. In peroxisomes, the inner contents are finely granular, but at times a crystalline core is visible by transmission electron microscope in the centre of peroxisomes.

This crystalline core is a crystallized protein known as catalase enzyme. Peroxisomes are usually found in kidney and liver cells.

Peroxisomes consists of catalase enzyme that catalyses the decomposition of hydrogen peroxide to water and oxygen. This gives the name ‘peroxisome’. As hydrogen peroxide is a by-product of some cell oxidations and is also highly toxic, so it must be eliminated from the cell.

Functions

Peroxisomes carry out some oxidative reactions like detoxification or removal of toxic substances from the cell.

Centrosome

Centrosome consists of two granule-like centrioles and it is not covered by any membrane. Centrioles are hollow and cylindrical structures that are made up of microtubules. Centrosomes are present only in animal cells. In plant cells, the polar caps perform functions similar to that of the centrioles.

Functions

Centrosome is involved in cell division in animal cells. At the time of cell division, centrioles move to the poles of cells and helps in the formation of spindle.

Chapter 1 The Fundamental Unit Of Life Master Your Test Question And Answers

Question 1. Name the following.

(a) Outer most layer of the cell wall connecting the two adjoining cells.

(b) Cell membrane is chemically made up of

(c) Fold of plasma membrane in bacterial cells.

(d) Component which is considered as dynamic part of cell.

(e) What happens to cell when placed in salt solution?

(f) Who proposed fluid mosaic model?

Answer: (a) Middle lamella (b) protein (c) mesosomes (d) nucleus (e) cell swells (f) S. J. Singer and G. L. Nicolson (1972)

Question 2. Define phagocytosis.
Answer: Intake of solid material by evagination of cell membrane on the periphery is known as phagocytosis.

Question 3. Define active transport.
Answer: Active transport is a speedy process. Diffusion is a slow process. This transport can move substances through a biological membrane against the concentration gradient and it is unidirectional in nature.

Question 4. Define exocytosis.
Answer: Exocytosis is the process by which the intracellular vesicles in the cytoplasm fuse with the plasma membrane and release their contents into the surrounding medium.

Question 5. Differentiate between diffusion and osmosis.
Answer:

Chapter 1 The Fundamental Unit Of Life Track Your Learning Questions and Answers

Question 1. Which of the following organelle is known as ‘suicidal bags’?

1. Peroxisomes
2. Lysosomes
3. Endosomes
4. Vacuoles

Answer. 2. Lysosomes

Question 2. Name the ‘powerhouse of the cell’.

1. Chloroplast
2. Chromoplast
3. Mitochondrion
4. Endoplasmic reticulum

Answer. 3. Mitochondrion

Question 3. In plant cells, Golgi apparatus is known as

1. Dictyosomes
2. Autosomes
3. Oxisomes
4. Golgi bodies

Answer. 1. Dictyosomes

Question 4. Light reaction of photosynthesis takes place in which part of chloroplast?

1. Stroma
2. Grana
3. Cristae
4. F1 particles

Answer. 2. Grana

Question 5. ______ serve as osmoregulatory organelles in protozoans.

1. Vacuoles
2. Vesicles
3. Lumen
4. Saccules

Answer. 1. Vacuoles

Question 6. Which one of the following has its own DNA?

1. Mitochondria
2. Dictyosome
3. Lysosome
4. Peroxisome

Answer. 1. Mitochondria

Question 7. The main arena of various types of activities of a cell is

1. Plasma membrane
2. Mitochondrion
3. Cytoplasm
4. Nucleus

Answer. 3. Cytoplasm

Question 8. In mitochondria, protons accumulate in the

1. Outer membrane
2. Inner membrane
3. Intermembrane space
4. Matrix

Answer. 3. Intermembrane space

Question 9. Which one of the following is not considered as a part of the endo-membrane system?

1. Golgi complex
2. Peroxisome
3. Vacuole
4. Lysosome

Answer. 2. Peroxisome

Question 10. Which one of the following organisms is not an example of eukaryotic cells?

1. Escherichia coli
2. Euglena viridis
3. Amoeba proteus
4. Paramecium caudatum

Answer. 1. Escherichia coli

Chapter 1 The Fundamental Unit Of Life Practice Exercises

NCERT Exemplar

Question 1. Which of the following can be made into crystal?

1. A bacterium
2. An amoeba
3. A virus
4. A sperm

Answer. 3. A virus

Question 2. A cell will swell up if

1. The concentration of water molecules in the cell is higher than the concentration of water molecules in surrounding medium.
2. The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell.
3. The concentration of water molecules is same in the cell and in the surrounding medium.
4. Concentration of water molecules does not matter.

Answer. 2. The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell.

Question 3. Chromosomes are made up of

1. DNA
2. Protein
3. DNA and protein
4. RNA

Answer. 3. DNA and protein

Question 4. Which of these options are not a function of ribosomes?

(1) It helps in the manufacture of protein molecules.

(2) It helps in the manufacture of enzymes.

(3) It helps in the manufacture of hormones.

(4) It helps in the manufacture of starch molecules.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and (1)

Answer. 3. (3) and (4)

Question 5. Which of these is not related to endoplasmic reticulum?

1. It behaves as transport channel for proteins between nucleus and cytoplasm.
2. It transports materials between various regions in cytoplasm.
3. It can be the site of energy generation.
4. It can be the site for some biochemical activities of the cell.

Answer. 3. It can be the site of energy generation.

Question 6. Following are a few definitions of osmosis, soread carefully and select the correct definition.

1. Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane.
2. Movement of solvent molecules from its higher concentration to lower concentration.
3. Movement of solvent molecules from higher concentration to lower concentration of solution through a permeable membrane.
4. Movement of solute molecules from lower concentration to higher concentration of solution through a semipermeable membrane.

Answer. 1. Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane.

Question 7. Plasmolysis in a plant cell is defined as

1. Breakdown (lysis) of plasma membrane in hypotonic medium.
2. Shrinkage of cytoplasm in hypertonic medium.
3. Shrinkage of nucleoplasm
4. None of the above

Answer. 2. Shrinkage of cytoplasm in hypertonic medium.

Question 8. Which of the following is covered by a single membrane?

1. Mitochondria
2. Vacuole
3. Lysosome
4. Plastid

Answer. 2. Vacuole

Question 9. Find out the false sentence.

1. Golgi apparatus is involved with the formation of lysosomes.
2. Nucleus, mitochondria and plastid have DNA and hence, they are able to make their own structural proteins.
3. Mitochondria is said to be the power house of the cell as ATP is generated in them.
4. Cytoplasm is known as protoplasm.

Answer. 1. Golgi apparatus is involved with the formation of lysosomes.

Question 10. Find out the correct sentence.

1. Enzymes packed in lysosomes are made through RER (rough endoplasmic reticulum).
2. Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein, respectively.
3. Endoplasmic reticulum is related with the destruction of plasma membrane.
4. Nucleoid is present inside the nucleoplasm of eukaryotic nucleus.

Answer. 1. Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein, respectively.

Question 11. Which cell organelle plays a crucial role in detoxifying many poisons and drugs in a cell?

1. Golgi apparatus
2. Lysosomes
3. Smooth endoplasmic reticulum
4. Vacuoles

Answer. 3. Smooth endoplasmic reticulum

Question 12. The proteins and lipids, essential for building the cell membrane are manufactured by

1. Rough endoplasmic reticulum
2. Golgi apparatus
3. Plasma membrane
4. Mitochondria

Answer. 1. Rough endoplasmic reticulum

Question 13. The undefined nuclear region of prokaryotes are also known as

1. Nucleus
2. Nucleolus
3. Nucleic acid
4. Nucleoid

Answer. 4. Nucleoid

Question 14. The cell organelle involved in forming complex sugars from simple sugars are

1. Endoplasmic reticulum
2. Ribosomes
3. Plastids
4. Golgi apparatus

Answer. 4. Golgi apparatus

Question 15. Which out of the following is not a function of vacuole?

1. Storage
2. Providing turgidity and rigidity to the cell.
3. Waste excretion
4. Locomotion

Answer. 4. Locomotion

Question 16. Amoeba acquires its food through a process, termed as

1. Exocytosis
2. Endocytosis
3. Plasmolysis
4. Exocytosis and endocytosis

Answer. 2. Endocytosis

Question 17. The cell wall of which one of these is not made up of cellulose?

1. Bacteria
2. Hydrilla
3. Mango tree
4. Cactus

Answer. 1. Bacteria

Question 18. Silver nitrate solution is used to study

1. Endoplasmic reticulum
2. Golgi apparatus
3. Nucleus
4. Mitochondria

Answer. 2. Golgi apparatus

Question 19. Organelle other than nucleus, containing DNA is

1. Endoplasmic reticulum
2. Golgi apparatus
3. Mitochondria
4. Lysosome

Answer. 3. Mitochondria

Question 20. Kitchen of the cell is

1. Mitochondria
2. Endoplasmic reticulum
3. Chloroplast
4. Golgi apparatus

Answer. 3. Chloroplast

Question 21. Lipid molecules in the cell are sythesized by

1. Smooth endoplasmic reticulum
2. Rough endoplasmic reticulum
3. Golgi apparatus
4. Plastids

Answer. 1. Smooth endoplasmic reticulum

Question 22. Cell arising from pre-existing cell was stated by

1. Haeckel
2. Virchow
3. Hooke
4. Schleiden

Answer. 2. Virchow

Question 23. Cell theory was given by

1. Schleiden and Schwann
2. Virchow
3. Hooke
4. Haeckel

Answer. 1. Schleiden and Schwann

Question 24. The only cell organelle seen in prokaryotic cell is

1. Mitochondria
2. Ribosomes
3. Plastids
4. Lysosomes

Answer. 2. Ribosomes

Question 25. Organelle without a cell membrane is

1. Ribosome
2. Golgi apparatus
3. Chloroplast
4. Nucleus

Answer. 1. Ribosome

Question 26. 1 μm is

1. 10^-6 m
2. 10^-9 m
3. 10^-10 m
4. 10^-3 m

Answer. 1. 10^-6 m

Question 27. Lysosome arises from

1. Endoplasmic reticulum
2. Golgi apparatus
3. Nucleus
4. Mitochondria

Answer. 2. Golgi apparatus

Question 28. Living cells were discovered by

1. Robert Hooke
2. Purkinje
3. Leeuwenhoek
4. Robert Brown

Answer. 3. Leeuwenhoek

Question 29. Select the odd one out from the following.

1. The movement of water across a semipermeable membrane is affected by the amount of substances dissolved in it.
2. Membranes are made of organic molecules like proteins and lipids.
3. Molecules soluble in organic solvents can easily pass through the membrane.
4. Plasma membranes contain chitin sugar in plants.

Answer. 4. Plasma membranes contain chitin sugar in plants.

Chapter 1 The Fundamental Unit Of Life Classroom Corner

Fill in the Blanks

Question 1. Scientist credited with the discovery of cell __________.
Answer. Robert Hooke

Question 2. World’s largest single-celled organism __________.
Answer. Caulerpa taxifolia

Question 3. Largest cell in the human body __________.
Answer. Ovum

Question 4. Smallest cell in the human body __________.
Answer. Sperms

Question 5. Proposed cell theory in animals __________.
Answer. Theodor Schwann in 1839

Question 6. Father of microbiology __________.
Answer. Anton van Leeuwenhoek

Question 7. Energy stored in mitochondria is in the form of __________.
Answer. ATP (Adenosine triphosphate)

Question 8. Groups of ribosomes in the cell __________.
Answer. Polysomes

Question 9. Plastids present in flowers and fruits _______.
Answer. Leucoplasts

Question 10. Considered as kitchen of cell __________.
Answer. Chloroplasts

 

 

Chapter 1 The Fundamental Unit Of Life Match The Columns

Question 1.

1. A-3, B-5, C-1, D-2, E-4
2. A-1, B-2, C-3, D-4, E-5
3. A-5, B-4, C-3, D-2, E-1
4. A-4, B-1, C-2, D-5, E-3

Answer. 1. A-3, B-5, C-1, D-2, E-4

Question 2.

Select the correct option.

1. A-1, B-2, C-3, D-4, E-5
2. A-5, B-4, C-3, D-2, E-1
3. A-4, B-5, C-1, D-3, E-2
4. A-5, B-3, C-1, D-4, E-2

Answer. 3. A-4, B-5, C-1, D-3, E-2

Question 3.

Select the correct option.

1. A-3, B-2, C-3, D-1, E-5
2. A-5, B-4, C-1, D-2, E-3
3. A-4, B-5, C-1, D-3, E-2
4. A-4, B-3, C-1, D-5, E-2

Answer. 3. A-4, B-5, C-1, D-3, E-2

Question 4.

Select the correct option.

1. A-1, B-2, C-3, D-4, E-5
2. A-5, B-4, C-1, D-2, E-3
3. A-4, B-5, C-1, D-3, E-2
4. A-4, B-5, C-3, D-1, E-2

Answer. 3. A-4, B-5, C-1, D-3, E-2

Question 5.

Select the correct option.

1. A-1, B-2, C-3, D-4
2. A-1, B-4, C-3, D-2
3. A-3, B-4, C-1, D-2
4. A-2, B-4, C-3, D-1

Answer. 3. A-3, B-4, C-1, D-2

Chapter 1 The Fundamental Unit Of Life Long Answer Type Question And Answers

Question 1. Discuss the differences between cell wall and plasma membrane.
Answer.

The differences between cell wall and plasma membrane:

Question 2. How does an amoeba obtain its food?
Answer.

An Amoeba Obtain Its Food As Follows:

Amoeba obtains food using temporary fingerlike extensions on the cell surface which fuse over the food particle forming a food-vacuole. Complex substances are broken down into simpler ones inside the food vacuole which then diffuses into the cytoplasm. The remaining undigested material is moved to the surface of the cell and is thrown out resulting in excretion.

Read and Learn More NEET Foundation Long Answer Questions

Question 3. Discuss the differences between mitochondria and chloroplast.
Answer.

The differences between mitochondria and chloroplast:

Question 4. Explain the functions of lysosomes.
Answer.

The functions of lysosomes:

• Lysosomes act as intracellular digestive system by destroying any foreign material that enters the cell and hence, these are called digestive bags. By doing this, they protect the cells from any harmful effect of foreign material such as from bacterial infection.
• Lysosomes remove the worn out cellular organelles by digesting them so that new replacements are done. By doing this, they remove the cell debris. Thus, lysosomes act as a type of garbage disposal system of the cell. These are also known as demolition squads, scavengers and cellular housekeepers.
• At the time of breakdown of cell structure, lysosomes may burst and the enzymes released eat up their own cells. Thus, lysosomes are also known as suicidal bags of a cell.

Question 5. Discuss the functions and types of ribosomes.
Answer.

The functions and types of ribosomes:

• Function: Ribosomes play a crucial role in the synthesis of proteins. These are the factories of protein in a cell. One ribosome cannot perform protein synthesis. In 1963, Gric and Hall published the detailed role of polyribosome in protein synthesis and showed that active units are no individual ribosome, instead a group of these units are known as polyribosomes.
• Types of ribosomes: Basically, there are two types of ribosomes, such as 70S and 80S ribosomes. Here, S denotes Svedberg unit, which is the sedimentation coefficient that depicts how fast cell organelle sediments in an ultracentrifuge. Sedimentation coefficients cannot be additive.

Question 6. Discuss the differences between smooth endoplasmic reticulum and rough endoplasmic reticulum.
Answer.

The differences between smooth endoplasmic reticulum and rough endoplasmic reticulum:

Question 7. Discuss the structure of nucleus.
Answer.

The structure of nucleus:

The nucleus is membrane-bounded, centrally located, spherical structure present in the eukaryotic cell. There are two nuclear membranes forming a nuclear envelope. There is a space between two nuclear membranes, which is connected to a system of membranes known as endoplasmic reticulum (ER).

The nuclear envelope makes the nucleus distinct from the cytoplasm. It also contains many pores called nuclear pores and consists of the liquid ground substance called nucleoplasm. Nuclear pores permit the transfer of substances between the nucleoplasm and the cytoplasm.

The nucleoplasm consists of the nucleolus and chromatin material. The nucleolus is not bounded by any membrane, and is rich in protein and RNA (ribonucleic acid), and thus, it acts as the site for ribosome production. Ribosomes help in protein synthesis in the cytoplasm.

Question 8. Discuss the differences between nucleus and nucleoid.
Answer.

The differences between nucleus and nucleoid:

Chapter 1 The Fundamental Unit Of Life Short Answer Type Question And Answers

Question 1. Discuss the structure and function of the plasma membrane.
Answer.

The structure and function of plasma membrane:

Delicate, elastic, and selectively permeable membrane. The membrane is almost made up of 75% phospholipids. It consists of proteins, cholesterol and polysaccharides. Membrane is a semipermeable or selectively permeable membrane. It gives shape to cell and regulates the movement of molecules in and out of the cell.

Question 2. Define diffusion and osmosis.
Answer.

Diffusion And Osmosis:

Diffusion is the net movement of solute particles from a region of high concentration to the region of low concentration. Osmosis is the passage of water or solvent from a region of high solvent concentration through a semipermeable membrane to a region of low solvent concentration.

Question 3. How do substances like CO₂ and water move in and out of the cell? Discuss.
Answer.

Movement Of substances like CO₂ and water move in and out of the cell:

The substances like CO₂ and water move in and out of a cell through the process called diffusion from the region of concentrated region to low concentrated one. When the concentration of carbon dioxide and water is higher in external environment than that inside the cell, CO₂ and water moves inside the cell. When the concentration outside the cell is low but it is high inside the cell, they move outwards.

Question 4. Discuss the difference between endocytosis and exocytosis.
Answer.

The difference between endocytosis and exocytosis:

Question 5. Why the plasma membrane is called a selectively permeable membrane?
Answer.

The plasma membrane is called a selectively permeable membrane:

Plasma membrane is called a selectively permeable membrane because it regulates the movement of substances from within to outside of the cell. This means that the plasma membrane allows the entry of some substances while preventing the movement of some other substance.

Question 6. Discuss the differences between active transport and diffusion.
Answer.

The differences between active transport and diffusion:

Question 7. Discuss the function of Golgi apparatus.
Answer.

The function of Golgi apparatus:

• Golgi apparatus acts as an assembly area for the storage, processing and packaging of various cellular secretions.
• It is involved in the synthesis of cell wall, plasma membrane and lysosomes

Question 8. Discuss why mitochondria is known as the power house of the cell.
Answer.

Mitochondria is known as the power house of the cell:

Mitochondria are known as the powerhouse of cells because the energy required for various chemical activities needed to support life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.

Question 9. What are dictyosomes?
Answer.

Dictyosomes:

In plant cells, Golgi apparatus is present in the form of freely distributed subunits called dictyosomes.

Question 10. Why are lysosomes known as suicide bags?
Answer.

Lysosomes known as suicide bags:

Lysosomes are called suicide bags because in case of any disturbance of their cellular metabolism, they release their own enzymes to digest their own cell.

Question 11. Where are proteins synthesized inside the cell?
Answer.

The proteins are synthesized in the ribosome.

Question 12. Discuss the characteristic features of peroxisomes and lysosomes.
Answer.

The characteristic features of peroxisomes and lysosomes:

Question 13. What are the characteristic differences between nucleus and nucleolus?
Answer.

The characteristic differences between nucleus and nucleolus:

Question 14. What would happen to the life of a cell if there was no Golgi apparatus?
Answer.

Golgi apparatus performs the function of a storage modification and packaging of products. If Golgi apparatus is not there, then the materials synthesized by cell will not be packaged and transported.

Question 15. Why the plasma membrane is called a selectively permeable membrane?
Answer:

The plasma membrane is called a selectively permeable membrane:

Plasma membrane is called a selectively permeable membrane because it regulates the movement of substances from within to outside of the cell. Selectively permeable describes the extreme selective nature of a membrane, wherein it specifically chooses certain molecules to pass. So, plasma membrane allows the entry of some substances while preventing the movement of some solutes.

Question 16. Who proposed the model called fluid mosaic model to explain the structure of functional cell membranes or plasma membranes?
Answer:

S. J. Singer and G. L. Nicolson (1972).

Question 17. Can you name the two organelles we have studied that contain their own genetic material?
Answer:

Mitochondria and plastids.

Question 18. If the organization of a cell is destroyed due to some physical or chemical influence, then what will happen?
Answer:

The organization of a cell is destroyed due to some physical or chemical influence:

If the organization of a cell is destroyed due to some physical or chemical influence then the cell will not be able to perform its basic functions, like digestion, excretion, respiration, etc. This may stop all the life activities and may come to an end.

Question 19. What is diffusion?
Answer:

Diffusion:

Diffusion is the net movement of solute particles from a region of high concentration to the region of low concentration.

Question 20. What would happen if the plasma membrane ruptures or breaks down?
Answer:

The cell will not be able to exchange material from its surroundings by diffusion. Due to this process, the protoplasmic material will disappear and the cell will die.

Chapter 1 The Fundamental Unit Of Life Multiple Choice Question And Answers

Direction: Choose the correct option for each questions. There is only one correct response for each question.

Question 1. The study of cell structure under microscope is

1. Cytology
2. Cell biology
3. Cytochemistry
4. Anatomy

Answer. 1. Cytology

Question 2. Which of the following does not have cellular structure?

1. PPLO
2. Rickettsia
3. Viruses
4. Archaebacteria

Answer. 3. Viruses

Question 3. The smallest animal egg is of

1. Ostrich
2. Duck
3. Human female
4. Hen

Answer. 3. Human female

Read and Learn More NEET Foundation Multiple Choice Questions

Question 4. Protoplasm without nucleus is called

1. Cytoplasm
2. Ectoplasm
3. Protoplasm
4. Endoplasm

Answer. 1. Cytoplasm

Question 5. Hardness of woody tissue is due to

1. Cellulose
2. Silica
3. Lignin
4. Suberin

Answer. 3. Lignin

Question 6. A well-organized nucleus is present in

1. Prokaryotes
2. Eukaryotes
3. Bacteria
4. Both (a) and(c)

Answer. 2. Eukaryotes

Question 7. Human egg is larger than human sperm because it has

1. Larger nucleus
2. More membrane
3. More cytoplasm
4. All of these

Answer. 3. More cytoplasm

Question 8. Within a cell, the site of respiration (oxidation) is the

1. Ribosome
2. Golgi apparatus
3. Mitochondria
4. Endoplasmic reticulum

Answer. 3. Mitochondria

Question 9. Which of the following is called ‘Suicidal bag’?

1. Centrosome
2. Lysosome
3. Mesosome
4. Chromosome

Answer. 2. Lysosome

Question 10. Double membrane is absent in

1. Mitochondrion
2. Chloroplast
3. Nucleus
4. Lysosome

Answer. 4. Lysosome

Question 11. The cell organelle found only in plant is

1. Golgi apparatus
2. Mitochondria
3. Plastids
4. Ribosomes

Answer. 3. Plastids

Question 12. Organisms lacking nucleus and membrane bound organelles are called

1. Diploids
2. Prokaryotes
3. Haploids
4. Eukaryotes

Answer. 2. Prokaryotes

Question 13. Animal cell is limited by

1. Plasma membrane
2. Shell membrane
3. Cell wall
4. Basement membrane

Answer. 1. Plasma membrane

Question 14. The network of endoplasmic reticulum is present in the

1. Nucleus
2. Nucleolus
3. Cytoplasm
4. Chromosome

Answer. 3. Cytoplasm

Question 15. Lysosome are reservoirs of

1. Fat
2. RNA
3. Secretory glycoprotein
4. Hydrolytic Enzymes

Answer. 4. Hydrolytic Enzymes

Question 16. The membrane surrounding the vacuole of a plant cell is called

1. Tonoplast
2. Plasma membrane
3. Nuclear membrane
4. Cell wall

Answer. 1. Tonoplast

Question 17. Cell secretion is done by

1. Plastids
2. ER
3. Golgi apparatus
4. Nucleolus

Answer. 3. Golgi apparatus

Question 18. Centrioles are associated with

1. DNA synthesis
2. Reproduction
3. Respiration
4. Spindle formation

Answer. 4. Spindle formation

Question 19. Ribosomes are the centre for

1. Respiration
2. Photosynthesis
3. Protein synthesis
4. Fat synthesis

Answer. 3. Protein synthesis

Question 20. Plastid which can form all other types of plastids is

1. Leucoplast
2. Amyloplast
3. Chloroplast
4. Chromoplast

Answer. 1. Leucoplast

Question 21. A plant cell becomes turgid due to

1. Plasmolysis
2. Exosmosis
3. Endosmosis
4. Electrolysis

Answer. 3. Endosmosis

Question 22. Solute concentration is higher in the external solution

1. Hypotonic
2. Hypertonic
3. Isotonic
4. None of these

Answer. 2. Hypertonic

Question 23. A cell placed in hypertonic solution will

1. Shrink
2. Show plasmolysis
3. Swell up
4. No change in shape or size.

Answer. 3. Swell up

Question 24. The radiant energy of sunlight is converted to chemical energy and is stored as

1. AMP
2. ATP
3. ADP
4. APP

Answer. 2. ATP

Question 25. Which of the following organelle does not have membrane?

1. Ribosome
2. Nucleus
3. Chloroplast
4. Mitochondria

Answer. 1. Ribosome

Question 26. Root hair absorbs water from soil through

1. Osmosis
2. Active transport
3. Diffusion
4. Endocytosis

Answer. 1. Osmosis

Question 27. The number of lenses in compound light microscope is

1. 3
2. 2
3. 4
4. 1

Answer. 2. 2

Question 28. Identify the human cells which lack nucleus

1. Platelets
2. WBC
3. RBC
4. Nerve cells

Answer. 3. RBC

Question 29. Which of the following cellular part possess a double membrane?

1. Nucleus
2. Chloroplast
3. Mitochondrion
4. All of the above

Answer. 4. All of the above

Question 30. Cristae and oxysomes are associated with

1. Mitochondria
2. Plastids
3. Golgi apparatus
4. Plasma membrane

Answer. 1. Mitochondria

Question 31. Genetic information is stored in

1. RNA
2. DNA
3. Ribosomes
4. Lysosomes

Answer. 2. DNA

Question 32. Animal cells have

1. Either few small vacuoles or may be absent
2. One large vacuole
3. Many large vacuoes
4. Few small vacuoles

Answer. 1. Either few small vacuoles or may be absent

Question 33. Cell organelle that acts as supporting skeletal framework of the cell is

1. Golgi apparatus
2. Nucleus
3. Mitochondria
4. ER

Answer. 4. ER

Question 34. What would happen if lysosomes get ruptured inside the cells in which they are present?

1. Cells will swell
2. Cells will die
3. Cells will shrink
4. Nothing would happen

Answer. 2. Cells will die

Question 35. The cell wall of plant is chiefly composed of

1. Hemicellulose
2. Phospholipids
3. Cellulose
4. Proteins

Answer. 3. Cellulose

Question 36. Which of the following are characteristics of unicellular organisms?

(1) There is no division of labour.

(2) Life span of organism is long.

(3) Reproduction consumes the whole cell.

(4) Single cell performs one or few activities of the organism.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (1) and (3)
4. (4) and (1)

Answer. 3. (1) and (3)

Question 37. Which of the following are properties of a light microscope?

(1) It uses beams of electrons to illuminate objects.

(2) It uses beams of light to illuminate the object.

(3) Internal vacuum is not required.

(4) It uses glass lenses.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (2), (3) and (4)
4. (1), (3) and (4)

Answer. 3. (2), (3) and (4)

Question 38. Which of the following are characteristics of prokaryotic cells?

(1) Nucleolus is absent.

(2) It contains single chromosome.

(3) Cell division occurs by mitotic or meiotic cell division.

(4) Size of cell is generally large (5.100 mm).Select the correct option.

1. (1) and (4)
2. (1) and (2)
3. (1), (2) and (3)
4. (3) and (4)

Answer. 2. (1) and (2)

Question 39. Which of these are not the features of organelles?

(1) They may be external or internal to body of an organism.

(2) They coordinate to produce the cell.

(3) They are found in all eukaryotic cells.

(4) They are macroscopic.

Select the correct option.

1. (1) and (2)
2. (4) and (3)
3. (1) and (4)
4. (2) and (3)

Answer. 3. (1) and (4)

Question 40. Which of these options are not functions of ribosomes?

(1) It helps in the manufacture of protein molecules.

(2) It helps in the manufacture of enzymes.

(3) It helps in the manufacture of hormones.

(4) It helps in the manufacture of starch molecules.

Select the correct option:

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and (1)

Answer. 3. (3) and (4)

Question 41. Osmosis __________________

(1) is the spontaneous movement of water molecules through a selective permeable membrane (for example, plasma membrane).

(2) can occur in any medium.

(3) occurs only in liquid medium.

(4) does not require semipermeable membrane.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and (1)

Answer. 4. (4) and (1)

Question 42. Endocytosis is __________________

(1) intake of extra-cellular fluid, droplets and macromolecules.

(2) intake of extracellular particles.

(3) growth of plasma membrane around the particle as pseudopodia.

(4) a nutritive process.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and (1)

Answer. 4. (4) and (1)

Question 43. Nucleus __________________

(1) is without a covering membrane.

(2) represents the whole eukaryotic complex that contains the genetic information.

(3) is covered by a two membrane envelope.

(4) is a component of nucleoid.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and 1

Answer. 2. (2) and (3)

Question 44. Chloroplasts __________________

(1) are green plastids

(2) are sites of photosynthesis

(3) are non-green coloured plastids

(4) do not contain lamellae

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and (1)

Answer. 1. (1) and (2)

Question 45. Chromosomes are made up of ______________

(1) DNA

(2) Protein

(3) O₂

(4) CO₂

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (4) and (1)

Answer. 1. (1) and (2)

Question 46. Find out the false statement from the following.

(1) Cytoplasm is also called protoplasm.

(2) Mitochondria is the powerhouse of the cell.

(3) Golgi apparatus is involved with the formation of lysosomes.

(4) Ribosomes do not help in protein synthesis.

Select the correct option.

1. (1) and (2)
2. (1) and (3)
3. (3) and (4)
4. (1) and (4)

Answer. 4. (1) and (4)

Question 47. Who amongst the following were contributors to the cell theory?

(1) Theodor Schwann

(2) Matthias Schleiden

(3) Robert Hooke

(4) Robert Brown

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (1) and (4)

Answer. 1. (1) and (2)

Question 48. Elephants eat grass and both have cells.

Read the following sentences regarding cells, and identify the correct ones.

(1) Grass cells have cell walls and vacuoles.

(2) Glass cells have cilia and chloroplast.

(3) Elephant cells are bigger than grass cells.

(4) Elephant cells have cell membrane and mitochondria.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (1) and (4)

Answer. 4. (1) and (4)

Question 49. A mature plant cell has

(1) Cell wall

(2) Plastids

(3) Centrioles

(4) Prominent golgi apparatus

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (3) and (4)
4. (1) and (4)

Answer. 1. (1) and (2)

Question 50. Mitochondria

(1) Powerhouse of the cell

(2) Green in colour

(3) Performs oxidation of food.

(4) Consumes CO₂ and liberates O₂.

Select the correct option.

1. (1) and (2)
2. (2) and (3)
3. (1) and (3)
4. (1) and (4)

Answer. 3. (1) and (3)

Question 51. A major site for synthesis of lipids is

1. Rough endoplasmic reticulum
2. Smooth endoplasmic reticulum
3. Symplast
4. Nucleoplasm

Answer. 2. Smooth endoplasmic reticulum

Question 52. Which structure perform the function of mitochondria in bacteria?

1. Nucleoid
2. Ribosomes
3. Cell wall
4. Mesosomes

Answer. 4. Mesosomes

Question 53. The important site for the formation of glycoproteins and glycolipids is

1. Golgi apparatus
2. Plastid
3. Lysosome
4. Vacuole

Answer. 1. Golgi apparatus

Question 54. In eubacteria, cellular component that resembles eukaryotic cells is

1. Nucleus
2. Ribosomes
3. Cell wall
4. Plasma membrane

Answer. 4. Plasma membrane

Question 55. Peptide synthesis inside a cell takes place in

1. Mitochondria
2. Chromoplast
3. Ribosomes
4. Chloroplast

Answer. 3. Ribosomes

Question 56. Ribosomal RNA is actively synthesized in

1. Lysosomes
2. Nucleolus
3. Nucleoplasm
4. Ribosomes

Answer. 2. Nucleolus

Question 57. Nuclear membrane is absent in

1. Penicillium
2. Agaricus
3. Volvox
4. Nostoc

Answer. 4. Nostoc

Question 58. True nucleus is absent in

1. Anabaena
2. Mucor
3. Vaucheria
4. Volvox

Answer. 1. Anabaena

Question 59. Which of the following is not an inclusion body found in prokaryotes?

1. Phosphate granule
2. Cyanophycean granule
3. Glycogen granule
4. Polysome

Answer. 4. Polysome

Question 60. Which of the following are not membrane-bound?

1. Ribosome
2. Lysosome
3. Mesosomes
4. Vacuole

Answer. 1. Ribosome

Question 61. Which of the following structures is not found in prokaryotic cell?

1. Ribosomes
2. Mesosomes
3. Plasma membrane
4. Nuclear envelope

Answer. 4. Nuclear envelope

Question 62. Cell organelle containing hydrolytic enzymes is

1. Microsome
2. Ribosome
3. Mesosome
4. Lysosome

Answer. 4. Lysosome

Question 63. Who proposed the fluid mosaic model of plasma membrane?

1. Camillo Golgi
2. Schleiden and Schwann
3. Singer and Nicolson
4. Robert Brown

Answer. 3. Singer and Nicolson

Question 64. What is a tonoplast?

1. Outer membrane of mitochondria.
2. Inner membrane of chloroplast.
3. Membrane boundary of the vacuole of plant cells.
4. Cell membrane of plant cell.

Answer. 3. Membrane boundary of the vacuole of plant cells.

Question 65. Satin used to visualize mitochondria is

1. Fast green
2. Safranin
3. Acetocarmine
4. Janus green

Answer. 4. Janus green

Question 66. Who refined the cell theory?

1. Schleiden
2. Schwann
3. Rudolf Virchow
4. Robert Hooke

Answer. 3. Rudolf Virchow

Question 67. Example/s of prokarotic cells is/are

1. Bacteria
2. Kidney cells
3. Interstitial cells
4. Cork cells

Answer. 1. Bacteria

Question 68. In prokaryotic cells, ______ is present instead of nucleus.

1. Nucleosome
2. Nuclear pore
3. Nuclear envelope
4. Nucleoid

Answer. 4. Nucleoid

Question 69. A science student wants to view the plasma membrane and other cell organelles of a rabbit cell. Which of the following microscope should the student use?

1. Light microscope
2. Compound microscope
3. Dissecting microscope
4. Electron microscope

Answer. 4. Electron microscope

Question 70. Cell theory states that cells are structural and fundamental units of

1. Plants
2. Animals
3. Both plants and animals
4. Only microorganisms

Answer. 3. Both plants and animals

Question 71. The energy currency of cell is

1. Mitochondria
2. ATP
3. FAD
4. Glucose

Answer. 2. ATP

Question 72. Which of the following organelles is enclosed in a single membrane?

1. Nuclei
2. Lysosomes
3. Chloroplast
4. Mitochondria

Answer. 2. Lysosomes

Question 73. The electron microscope was developed by

1. Huxley
2. Knoll and Ruska
3. Purkinje
4. Robert Hooke

Answer. 2. Knoll and Ruska

Question 74. The idea of ‘Omnis Cellula e Cellula’ was given by

1. Scheiden
2. Rudolf Virchow
3. Purkinje
4. Schwann

Answer. 2. Rudolf Virchow

Question 75. The size of an organism is dependent on

1. Size of the cell
2. Number of cell
3. Both (a) and (b)
4. Shape of cells

Answer. 3. Both (a) and (b)

Chapter 2 Atoms And Molecules

For ages, ancient Indian and Greek philosophers wondered about the unseen and unknown form of matter. Around 500 bc, India, the idea of divisibility of matter took shape. Maharishi Kanad, An Indian philosopher, suggested that if we kept on diving matter (padarth), we will get smaller and smaller particles and ultimately, a time will come when the further division will not be possible and we will obtain the smallest particle of the matter.

He called these particles as parmanu. Pakudha Katyayama, another Indian philosopher, postulated that these exists in the combined form which is the reason for the varied forms of matter.

All matters are made up of atoms. Atoms do not exist independently. Atoms are further divided into ions and molecules. Molecules and ions collectively in large number forms matter.

Chapter 3 Atoms And Molecules Laws of Chemical Combination

A molecule is a group of atoms that are chemically bonded together and held by intermolecular force. The tiniest particle of an element which exists independently by inheriting all the characteristics of that substance is called a molecule.

Matter transforms from one state to the other under certain circumstances. This phenomenon takes place due to combination of two types of matter. This process of combination of different elements to form compounds takes place under certain rule.

Read and Learn More: NEET Foundation Notes

Chemistry is the study of the transformation of matter from one form to the other. These transformations often occur as a result of the combination of two different types of matter. The combination of different elements to form compounds is governed by certain basic rules. These rules are referred to as laws of chemical combination.

The rules are known as laws of chemical combination. The rules that aid the chemical combinations of elements are discussed below.

Law of Conservation of Mass

Law of conservation of mass was given by Antoine Lavoisier and verified by Landolt. According to this law, during a chemical reaction matter is neither created nor destroyed, it may change from one form to other. After a chemical reaction the total mass of materials is same as the total mass before reaction.

Greek Philosopher Democritus (460–370 bc) and Leucippus also worked on the idea of division of matter. According to them sub-division of matter is limited. Democritus named the individual particles as ’atoms’ meaning indivisible.

Law of Constant or Definite Proportion

Law of definite proportion was given by Joseph Proust who was a French chemist. According to the law, in a given compound the proportion of elements by weight will always remain same irrespective of the methods of preparation.

Law of Multiple Proportions

Law of multiple proportions was given by Dalton in 1803 and verified by Berzelius. According to this law, when more than one compound is formed by combining two elements the masses of these elements in the reaction are in the ratio of small whole numbers.

Law of Equivalent Proportion or Law of Reciprocal Proportion

Law of equivalent proportion was given by Ritcher. According to this law, the weights of two or more elements which separately react with same weight of a third element are also the weights of these elements which react with each other or in simple multiple of them.

Gay-Lussac’s Law of Gaseous Volumes

Gay-Lussac’s law of Gaseous volumes was given by Gay–Lussac in 1808 and is applicable only for gases. This law was based on experimental observation done by Gay-Lussac. According to the law, the production of gases takes place in a simple ratio by volume, temperature and pressure being constant.

It can be treated as another form of law of definite proportions. The only difference between these two is that Gay Lussac’s Law is stated with respect to volume while law of definite proportions is stated with respect to mass.

Avogadro’s Law

Avogadro in 1811 gave Avogadro’s law which states that equal volume of gas contains equal number of molecules, temperature and pressure being constant.

Example: 2 litres of hydrogen contains same number of molecules as 2 litres of oxygen, temperature and pressure being constant of both gases.

John Dalton’s Atomic Theory

Basic theory about nature of matter was given by the British chemist, John Dalton. His theory was on the fundamentals of laws of chemical combination. His theory explained law of conservation of mass and the law of definite proportions extensively.

He gave his atomic theory in 1808 according to which all matter (element, compound or mixture) is made up of small particles called atoms. The postulates of Dalton’s atomic theory are:

• Matter consists of very tiny particles called atoms.
• Atoms are of indivisible nature which cannot be created or destroyed in a chemical reaction.
• Mass and chemical properties of atoms of a given element are identical.
• Different element atoms have different masses and chemical properties.
• Compounds are formed by combining atoms in the ratio of small whole numbers.
• In a given compound, the relative number and kinds of atoms are constant.

Law of conservation of mass is related to Dalton’s fourth postulate. Every atom of an element has a definite mass. Rearrangement of atoms takes place in a chemical reaction. Thus after the reaction, mass of the product should remain the same. Law of definite proportions is explained in the fifth postulate.

A compound consists of matter having atoms of two or more elements in small whole number ratio. As the atoms have definite mass, the compound must have the elements in definite proportions by mass.

The Dalton’s atomic theory also predicted the new theories like law of multiple proportions  on the basis of his theory. The deduction of law of multiple proportions from atomic theory was important in convincing chemists of the validity of the theory.

So, Dalton’s atomic theory explains states that:

• All matter is made of atoms. Atoms are indivisible and indestructible.
• All atoms of a given element are identical in mass and properties
• Compounds are formed by a combination of two or more different kinds of atoms.
• A chemical reaction is an arrangement of atoms.

Modern atomic theory is, of course, a little more involved than Dalton’s theory but the essence of Dalton’s theory remains valid. Today we know that atoms can be destroyed via nuclear reactions but not by chemical reactions.

Many heretofore unexplained chemical phenomena were quickly explained by Dalton with his theory. Dalton’s theory quickly became the theoretical foundation in chemistry.

Symbols for every element were firstly used by Dalton in a particular way. His symbolization for an element defined a definite quantity of that element, i.e one atom of that element. Berzilius idea for the symbols of elements was to use one or two letters of the name of the element.

Initially the names of elements were derived from the name of the place where they were found for the first time.

Example: Copper was taken from Cyprus.

Some names were taken from specific colours.

Example: Gold was taken from the English word meaning yellow.

Modern Periodic Table

In recent times, IUPAC (International Union of Pure and Applied Chemistry) approves names of elements. Many of the symbols are the first one or two letters of the element’s name in English.

The first letterof a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase).

 

Chapter 3 Atoms And Molecules Track Your Learning Question And Answers

Question 1. ___________ is the study of the transformation of matter from one form to the other.
Answer. Chemistry

Question 2. Law of conservation of mass was given by Antoine Lavoisier and verified by Landolt. (True/False)
Answer. True

Question 3. Law of equivalent proportion was given by:

1. Ritcher
2. Joseph Proust
3. Gay–Lussac
4. Maharshi Kanad

Answer. 1. Ritcher

Question 4. Law of definite proportion was given by______________.
Answer. Joseph Proust

Chapter 3 Atoms And Molecules About Atom

An atom is the smallest unit of matter which has the chemical properties of the element. An atom has number of constituents which may vary according to the different elements. It means that atoms of different elements will be of different size.

The earlier thinkers considered atom to be the smallest reachable unit which cannot be broken down further. But, it is now a basic knowledge that atom can be broken into its constituents but these constituents do not have the chemical properties of the atom.

Size of the Atom

The atom is the smallest unit of the element. It is now known that atoms of different elements vary not only in mass but also in size. But, there is still no consensus on the shape of the atom. But as a general rule the shape of an atom is considered to be spherical. That is why the radius of the atom is discussed. The size of atom is measured in nanometre.

The magnified image of the atoms on the surface of the elements can be seen with the new technique called scanning tunneling microscopy (STM).

As we know, atoms are made up of three particles: protons, neutrons and electrons. Protons and neutrons are heavier than electrons and reside in the center of the atom, which is called the nucleus. Electrons are extremely lightweight and exist in a cloud orbiting the nucleus. The electron cloud has a radius 10,000 times greater than the nucleus.

Protons and neutrons have approximately the same mass. However, one proton weighs more than 1,800 electrons. Atoms always have an equal number of protons and electrons, and the number of protons and neutrons is usually the same as well. Adding a proton to an atom makes a new element, while adding a neutron makes an isotope, or heavier version, of that atom.

Atomic Number and Atomic Mass

Protons exist in the nucleus of an atom and the number of protons of an atom constitutes the atomic number. Its symbol representation is done by ’z’. Similar atomic number is possessed by all atoms of an element. Elements are defined by the number of protons they possess. So the total number of protons present in the nucleus of an atom is called atomic number.

Example: For hydrogen, z = 1, because in hydrogen atom, only one proton is present in the nucleus. Similarly, for carbon, z = 6.

On observation of properties of the subatomic particles of an atom, it can be concluded that the mass of an atom is due to neutrons and protons. They are found in nucleus of the atom hence called nucleons. So, the mass of an atom resides in its nucleus. The amount of the total number of protons and neutrons present in the nucleus of an atom is called atomic mass.

Example: Mass of carbon is 12 u because it has 6 protons and 6 neutrons, 6 u + 6 u = 12 u. Similarly, the mass of aluminium is 27 u (13 protons + 14 neutrons).

Atomic masses of a few elements

Valency

Electrons exist in different orbits and the electrons present in the outermost orbit are known as valence electrons. The outmost shells can contain maximum of 8 electrons as per Bohr and Bury. It was noticed in an atom with completely filled outermost shell show little chemical activity meaning their combining capacity or valency is zero.

The only exception to this rule is helium. It has two electrons in its outermost shell. Except this all the inert elements have 8 electrons in the outermost orbit.

So, valency is a tendency in an atom to achieve the state of stability by achieving 8 electrons in its outermost shell by receiving, leaving or sharing of electrons from other atoms. It simply means that if an atom has 1 electron in its last orbit it will have a tendency to lose this electron for achieving stability. So it will have valency of

1. On the other hand if an atom has 6 electrons in its last orbit it should be easier for this atom to take 2 electrons for the other atom instead of leaving 6 electrons. So, the valency will be 2.

Example: CO₂ is made up of 1 carbon and 2 oxygen atoms. Valency of carbon is 4 while valency of oxygen is 2. So, to be stable 1 carbon atom will have to combine with 2 oxygen atoms to form 1 molecule of carbon dioxide.

Chapter 3 Atoms And Molecules Master Your Test Question And Answers

Question 1. Name two elements which exists independently.
Answer.

Helium and neon are two elements which exists independently.

Question 2. Define an atom.
Answer.

Atom:

An atom is the smallest unit of matter which has the chemical properties of the element.

Question 3. What is atomic mass?
Answer.

Atomic Mass:

The amount of the total number of protons and neutrons present in the nucleus of an atom is called atomic mass.

Question 4. Define valency.
Answer.

Valency:

Valency is a tendency in an atom to achieve the state of stability by achieving 8 electrons in its outermost shell by receiving, leaving or sharing of electrons from other atoms.

Chapter 3 Atoms And Molecules Track Your Learning Question And Answers

Question 1. __________ are basic building blocks of matter.
Answer. Atoms

Question 2. The total number of protons present in the nucleus of an atom is called_________.
Answer. Atomic number

Question 3. Electrons present in the outermost orbit are known as_________.
Answer. Valence electrons

Question 4. Protons revolve around the nucleus of an atom (True/ False).
Answer. False

Chapter 3 Atoms And Molecules About Molecule

Molecules of elements: A molecule is made up of atoms. Molecules of elements are made up of same types of atoms. Some molecules may be made up of a single atom.

Example: Helium, But in most of the cases the molecules are made up of two or more atoms. The number of atoms needed to make a molecule is called as atomicity of that element.

Molecules of compounds: A compound is a molecule made up of 2 or more different types of atoms.

Example: 1 molecule of water contains 2 molecules of hydrogen and 1 molecule of oxygen. Similarly, 1 molecule hydrochloric acid contains 1 molecule of hydrogen and 1 molecule of chlorine.

Molecules of some compounds

Atomicity

It refers to the number of atoms present in one molecule of an element or substance.

For example one molecule of HCl has one atom of hydrogen and one atom of chlorine. So, the atomicity of HCl is 2. The molecules are called Monatomic, Diatomic or triatomic depending on the number of atoms present in it.

Atomicity of some elements

Ion

An ion is defined as an electrically charged atom or group of atoms formed by the loss or gain of one or more electrons. A positive ion is created by electron loss and a negative ion is created by an electron gain.

Example: Air conditioners, fluorescent lamps and printers, etc., are generators of positive ion or cation, which is very harmful for health.

On the other hand negative ions are in abundance in forests. The natural negative ions neutralize the harmful positive ions in the atmosphere as they attract dust particles and other pollutants.

Positively charged ion is called cation and a negative ion called anion.

Some common, simple and polyatomic ions

Chapter 3 Atoms And Molecules Master Your Test Question And Answers

Question 1. What are homonuclear molecules?
Answer.

Homonuclear molecules:

Homonuclear molecules are those molecules in which same type of atoms are present.

Example H₂, Cl₂ etc.

Question 2. What are heteronuclear molecules?
Answer.

Heteronuclear Molecules:

Heteronuclear molecules are those molecules in which different type of atoms are present.

Example, H₂O, CO₂ etc.

Question 3. What are polyatomic ions?
Answer.

Polyatomic ions:

A group of atoms that carry a charge is called polyatomic ion. Example NH4⁺, CO₃^2- etc.

Question 4. Why were the rehabilitation centres and health spas made in forest areas?
Answer.

The forests besides giving fresh and unpolluted air, also naturally provide negative ions which neutralises the harmful effects of positive ions.

Chapter 3 Atoms And MoleculesTrack Your Learning Question And Answers

Question 1. Positively charged ion is called ________.
Answer. Cation

Question 2. Air conditioners, fluorescent lamps and printers, etc., are generators of __________.
Answer. Ions

Question 3. If one walks to a forest, which type of ion he will find more naturally?

1. Negative
2. Positive
3. Both
4. None

Answer. 1. Negative

Question 4. ___________ refers to the number of atoms present in one molecule of an element or substance.
Answer. Atomicity

Chapter 3 Atoms And Molecules Writing Chemical Formulae

The chemical formula of a compound represents its chemical composition. A chemical formula essentially indicates 2 things:

• The elements which constitutes that compound and the number of each element in it.
• The number of each constituent.

The atoms of the elements are indicated by the symbols and the number is indicated as a subscript with the symbol.

Example: In CO₂, C and O are the symbols of carbon and oxygen respectively while 2 indicates that 2 atoms of oxygen have been used in the compound.

There are three fundamental rules of writing chemical formula:

• The valencies of the elements must balance.
• When a compound contains both metal and non-metal elements the name of metal comes first.Example: Sodium Chloride (NaCl)
• In polyatomic ion compounds, the ion is enclosed in bracket before writing the formula to indicate the ratio. In case the ion is mono-atomic then bracket is not required.

Formula of Simple Compound

For writing a formula for the simple compound the symbol and the valencies of the atoms are written and then the valencies are crossed with the atom to balance the formula.

Illustration 1: Figure explains that the valency of carbon atom is 4 while that of chlorine is 1. To balance the formula the valency is crossed with the symbol to write the correct formula.

Formulation of Ionic Compounds

When writing a formula with ionized atoms it should be kept in mind that the cation and anion should be balanced.

Illustration 2: The figure explains that the Aluminum atom has 3 positive charges while Oxygen atom has 2 negative charges. To balance this, 2 atoms of Al and 3 atoms of O are used to form neutralized Al₂O₃.

Chapter 3 Atoms And Molecules Master your Test Question And Answers

Question 1. What does a chemical formula tell us about?
Answer.

Chemical formula:

A chemical formula tells us about the elements present in a compound along with their number.

Question 2. State the chemical formula of the compound formed between Hydrogen and Sulphur.
Answer.

Chemical formula of the compound formed between Hydrogen and Sulphur:

Valency of Hydrogen = 1

Valency of Sulphur = 2

Compound of Hydrogen and Sulphur = H₂S

Question 3. An element ‘A’ forms a compound A²O³. What according to you is the valency of A?
Answer.

An element ‘A’ forms a compound A²O³.

The valency of A will be 3.

Question 4. An element has a valency of 2. What will be the formula for its oxide?
Answer.

An element has a valency of 2.

Valency of the element (X) = 2

Valency of Oxygen = 2

Formula for its oxide = XO

Chapter 3 Atoms And Molecules Track Your Learning Question And Answers

Question 1. When a compound contains both metal and non-metal elements the name of ___________ comes first.
Answer. Metal

Question 2. What does the chemical formula of a compound represent?

1. Physical composition
2. Chemical composition
3. Ions
4. Atomic number

Answer. 2. Chemical composition

Question 3. While writing a chemical formula, brackets are required in case of ____________ ions.
Answer. Polyatomic

Question 4. Atoms of the elements are indicated by the ____________ in a chemical formula.
Answer. Symbols

Chapter 3 Atoms And Molecules Molecular Mass and Mole Concept

The molecular mass is the sum of atomic masses of all the atoms present in the molecule. The relative mass of molecule is expressed in atomic mass unit (u). The formula unit mass is the sum of the atomic masses of all atoms in a formula unit of a compound. It is calculated in the way we calculate the molecular mass. We use formula unit for those substances which are made up of ions.

Atomic Mass Unit (u) is defined as a unit of mass used to express atomic and molecular weights, equal to one twelfth of the mass of an atom of carbon-12.

Example: Atomic mass of carbon is 12.0 u while atomic mass of oxygen atom is 16.0 u, so the molecular mass of 1 molecule of CO₂ will be 44.0 u (12.0 u + 16.0 u + 16.0 u).

Mole Concept

It is not necessary that all the substances are formed by joining of atoms. In practice 2 or more molecules can also be mixed to get new substances.

Example: 2 molecules of hydrogen combine with 1 molecule of oxygen to make 2 molecules of water. It is evident from this example that 2 hydrogen and 1 oxygen is the minimum required unit to create molecule of water.

In other words mole is the number of atoms in 12 grams of C-12. This is the basic counting unit for scientists.

1. The number of atoms in 12 gram of C-12 is 6.022 × 10²³. This is called Avogadro’s number.

2. When Avogadro number is divided by mole it becomes a constant known as Avogadro’s constant denoted by N_A ⋅ N_A = 6.02 × 10²³ mol^-1.

Example: Atomic mass of carbon (C) is 12 u.

This means 12 u C has only 1 atom of carbon.

12 g carbon has 1 mole atoms of carbon

Therefore, 12 gram carbon has 6.02 × 10²³ atoms of carbon.

Similarly, atomic mass of He (Helium) is 4 u

4 u He will have only 1 atom of He.

4 gram of He will have 1 mole atoms of He.

Therefore, 4 grams He has 6.02 × 10²³ atoms of He.

Molar Mass

Mass of 1 mole of substance is called molar mass.

Example: Atomic mass of He is 4 u

So 4 u of He = 1 atom of He

So 4 gram of He = 1 mole atom of He

Therefore, molar mass of He is 4 gram.

 

Chapter 3 Atoms And Molecules Track Your Learning Question And Answers

Question 1. 6.022 × 10²³ is the number of atoms in 12 g of ____________.
Answer. Carbon – 12

Question 2. Mass of 1 mole of substance is called ____________.
Answer. Molar mass

Question 3. 6.022 × 10²³ is called the ____________.
Answer. Avogadro’s number

Question 4. The relative mass of molecule is expressed in atomic mass unit (u). (True/False)
Answer. True

 

Chapter 3 Atoms And Molecules Classroom Corner

Fill in the Blanks

Question 1. Ozone is an example of __________ molecule.
Answer. Triatomic

Question 2. In water, the ratio of hydrogen and oxygen is __________.
Answer. 2:1

Question 3. The valency of nitrogen in NH3 is __________.
Answer. 3

Question 4. All noble gas molecules are __________ in nature.
Answer. Monoatomic

Question 5. The __________ is the sum of atomic masses of all the atoms present in the molecule.
Answer. Molecular Mass

Question 6. A __________ is a molecule made up of 2 or more different types of atoms.
Answer. Compound

Question 7. The number of atoms needed to make a molecule is called as __________ of that element.
Answer. Atomicity

Question 8. During a chemical reaction matter is neither created nor destroyed, it may change from one form to other, is explained by___________ law.
Answer. Conservation of Mass

Question 9. When there is more number of electrons than protons, the atom is called ________.
Answer. Anion

Question 10. __________ is a tendency in an atom to achieve the state of stability.
Answer. Valency

 

Chapter 3 Atoms And Molecules Match the Column

Question 1. Match the following and choose the correct code:

Select the correct option:

1. A-4, B-3, C-1, D-2
2. A-2, B-3, C-4, D-1
3. A-3, B-1, C-2, D-4
4. A-1, B-4, C-2, D-3

Answer. 3. A-3, B-1, C-2, D-4

Question 2. Match the following and choose the correct code:

Select the correct option:

1. A-4, B-1, C-2, D-3
2. A-3, B-4, C-1, D-2
3. A-2, B-3, C-4, D-1
4. A-4, B-2, C-1, D-3

Answer. 2. A-3, B-4, C-1, D-2

Question 3. Match the following and choose the correct code:

Select the correct option:

1. A-4, B-3, C-1, D-2
2. A-2, B-4, C-1, D-3
3. A-1, B-3, C-2, D-4
4. A-3, B-2, C-4, D-1

Answer. 1. A-4, B-3, C-1, D-2

Question 4. Match the following and choose the correct code:

Select the correct option:

1. A-4, B-3, C-2, D-1
2. A-2, B-1, C-4, D-3
3. A-3, B-2, C-1, D-4
4. A-3, B-4, C-2, D-1

Answer. 4. A-3, B-4, C-2, D-1

Question 5. Match the following and choose the correct code:

Select the correct option:

1. A-3, B-4, C-2, D-1
2. A-2, B-4, C-1, D-3
3. A-1, B-2, C-4, D-3
4. A-4, B-3, C-2, D-1

Answer. 2. A-2, B-4, C-1, D-3

Chapter 3 Atoms And Molecules Assertion Reasoning

For the following questions the options will remain the following:

1. Both A and R are correct and R is correct explanation of A.
2. Both A and R are correct but R is not a logical explanation of A.
3. A is correct but R is incorrect.
4. R is correct but A is incorrect.

Question 1. Assertion: The molecular mass expressed in grams is called gram molecular mass.
Reason: The molecular mass is equal to the sum of the masses of all the atoms of a molecule.

Answer. 2. Both A and R are correct but R is not a logical explanation of A.

Question 2. Assertion: Ion is a charged chemical particle.
Reason: An ion that carries a positive charge is called a cation and an ion that carries a negative charge is called an anion.

Answer. 1. Both A and R are correct and R is correct explanation of A.

Question 3. Assertion: Molar volume is the volume occupied by various moles of a gas under any conditions of temperature and pressure.
Reason: It is equal to 22.4 litres.

Answer. Both A and R are correct and R is correct explanation of A.

Chapter 3 Atoms And Molecules Comprehension Passage

An atom is defined as the smallest particle of an element which may or may not be capable of free existence. Atom of hydrogen, oxygen, nitrogen, etc., are highly reactive and do not exist in the Free State. They exist in the combined state with atoms of the same element one atoms of the other elements. Dalton was the first scientist to suggest specific symbols for different elements.

Symbols used by him also represented the quantity of the element, i.e., one atom of the element. The actual masses of the atoms are so small that it is difficult to determine the actual masses of individual atoms. For example, actual mass of an atom of hydrogen is found to be 1.673 × 10^-24 g which is extremely small.

However, it was found convenient to compare the masses of atoms of different element with some reference atom. The masses thus obtained are called relative atomic masses and the scale on which these masses are expressed is called atomic mass scale.

A molecule is the smallest particle of a compound which can exist freely under ordinary conditions and shows all the properties of that substance. Molecules of some elements are very big in size containing a large number of atoms linked together. For example, graphite and diamond contain an infinite number of carbon atoms linked together.

These elements are simply represented by their atomic symbols. A third crystalline form of carbon discovered recently contains 60 C-atoms linked together. It is represented by C₆₀ and is known as Buckminsterfullerene. Molecules of a compound are two or more atoms of different elements combined together in a definite proportion by mass to form a species that can exist freely.

As molecules are made up of two or more atoms of the same or different elements and each atom has a definite atom mass, therefore, molecular mass of a molecule of a substance can be calculated by adding atomic masses of all the atoms present in one molecule of the substance.

Questions:

Question 1. Molecule of a compound means ________.

1. Atoms are held together by a chemical bond.
2. To attract the shared pair of electrons.
3. Different elements combined together in a definite proportion by mass.
4. Compounds are formed by the combination of two or more non-metal atoms.

Answer. 3. Different elements combined together in a definite proportion by mass.

Question 2. Which of the following is true about Dalton’s symbols of elements?

1. Suggested the specific symbols for different elements.
2. Element is the relative mass of its atoms.
3. Substances made up of the same kind of atoms.
4. Atoms of the same element may have different masses.

Answer. 1. Suggested the specific symbols for different elements.

Question 3. Graphite and diamond contains ________.

1. Fixed number of carbon atoms.
2. Infinite number of carbon atoms.
3. Very small number of carbon atoms.
4. No carbon atoms.

Answer. 2. Infinite number of carbon atoms.

Question 4. How the carbon represents through the structure of Buckminsterfullerene?

1. C-12
2. C_a
3. CI
4. C₆₀

Answer. 4. C₆₀

Question 5. What is relative atomic mass?

1. Masses of atoms of different element with some reference atom.
2. Scale of the masses expressed.
3. Average atomic mass of an element.
4. Short method of representing an element.

Answer. 1. Scale of the masses expressed.

Chapter 3 Atoms And Molecules Long Answer Type Question And Answers

Question 1. State the postulates of Dalton’s atomic theory.
Answer.

The postulates of Dalton’s atomic theory are:

• Matter consists of very tiny particles calledatoms.
• Atoms are of indivisible nature whichcannot be created or destroyed in a chemical reaction.
• Mass and chemical properties of atoms of agiven element are identical.
• Different element atoms have differentmasses and chemical properties.
• Compounds are formed by combining atomsin the ratio of small whole numbers.
• In a given compound, the relative numberand kinds of atoms are constant.

Question 2. What are the fundamental rules of writing the chemical formula?
Answer.

There are three fundamental rules of writing chemical formula:

Read and Learn More NEET Foundation Long Answer Questions

• The valencies of the elements must balance.
• When a compound contains both metal and non-metal elements the name of metal comes first. Example: Sodium Chloride (NaCl)
• In poly-atomic ion compounds, the ion is enclosed in bracket before writing the formula to indicate the ratio. In case the ion is mono-atomic then bracket is not required.

Question 3. What does the Dalton’s theory explain? How is it different from modern atomic theory?
Answer.

Dalton’s Atomic theory explains that:

• All matter is made of atoms. Atoms are indivisible and indestructible.
• All atoms of a given element are identical in mass and properties
• Compounds are formed by a combination of two or more different kinds of atoms.
• A chemical reaction is an arrangement of atoms.

Modern atomic theory is, of course, a little more involved than Dalton’s theory but the essence of Dalton’s theory remains valid. Today we know that atoms can be destroyed via nuclear reactions but not by chemical reactions. Many heretofore unexplained chemical phenomena were quickly explained by Dalton with his theory. Dalton’s theory quickly became the theoretical foundation of chemistry.

Question 4. What does a chemical formula indicate?
Answer.

Chemical Formula:

The chemical formula of a compound represents its chemical composition.

A chemical formula essentially indicates 2 things:

• The elements which constitutes thatcompound and the number of each element in it.
• The number of each constituent.

The atoms of the elements are indicated by the symbols and the number is indicated as a subscript with the symbol.

Chapter 3 Atoms And Molecules Multiple Choice Question And Answers

Direction: Choose the correct option for each questions. There is only one correct response for each question.

Question 1. Who was the first Indian Philosopher who had postulated that matter is divisible?

1. Maharshi Kanad
2. Chanakya
3. Swami Vivekanada
4. Sarvapalli Radhakrishnan

Answer. 1. Maharshi Kanad

Question 2. Why is the symbol of silver written as Ag?

1. The symbol of silver is derived from the French name ‘Agiol’.
2. The symbol of silver is derived from the French name ‘Aglae’.
3. The symbol of silver is derived from the Latin name ‘Argentum’.
4. The symbol of silver is derived from the German name ‘Agapios’.

Answer. 3. The symbol of silver is derived from the Latin name ‘Argentum’.

Question 3. What do you mean by atomicity of a molecule?

1. The number of molecules in a substance.
2. The number of atoms present in one molecule of a substance.
3. The number of atoms bonded in a molecule of an element.
4. The mass of an atom of an element.

Answer. 2. The number of atoms present in one molecule of a substance.

Read and Learn More NEET Foundation Multiple Choice Questions

Question 4. What do you mean by saying that molecular mass of oxygen is 32?

1. 1/1837 times the mass of proton.
2. Molecule of O₂ is 32 times heavier as compared to 1/12th of the mass of an atom of C-12 isotope.
3. Molecule of O₂ is 8 times heavier as compared to 1/12th of the mass of an atom of C-12 isotope.
4. None of the above

Answer. 2. Molecule of O₂ is 32 times heavier as compared to 1/12th of the mass of an atom of C-12 isotope.

Question 5. If 100 g of calcium carbonate on heating produces 44 g of carbon dioxide, how much quick lime will be formed?

1. Quick lime will be 56 g
2. Quick lime will be 72 g
3. Quick lime will be 38 g
4. Quick lime will be 44 g

Answer. 1. Quick lime will be 56 g

Read more

Chapter 3 Atoms And Molecules Short Answer Type Question And Answers

Question 1. Calculate the molar mass of HNO₃. [N = 14, O = 16, H = 1]
Answer.

Given:

Molar mass of HNO₃.

H = 1 × 1 = 01

N = 14 × 1 = 14

O = 16 × 3 = 48

Total mass = 63 grams

Molar mass of HNO₃ = 63 grams.

Question 2. Calculate the formula mass of CaCl₂. [Ca = 40, Cl = 35.5]
Answer.

Given:

1(Ca) + 2(Cl) 40 + 2 × (35.5) = 111 u

The formula mass of CaCl₂ is 111 u.

Question 3. A certain non-metal X forms two oxides 1 and 2. The mass percentage of oxygen in oxide 1 (X4O6) is 43.7, which is same as that of X in oxide 2. Find the formula of the second oxide.

Answer.

Now 43.7 parts of oxygen in I corresponds to = 6 oxygen atoms

Therefore, 56.3 parts of oxygen in II corresponds to

⇒ \(\frac{6 \times 56.3}{43.7}=7.730 \text { atoms }\)

Also 56.3 parts of X in 1 correspond to = 4 X atom

Therefore, 43.7 parts of X in 2 will correspond to

⇒ \(=\frac{4 \times 43.7}{56.3} \times 3.1 \times \text { atoms }\)

Now the atomic ration X : O in the second

Oxide = \(\frac{3.1}{3.1}: \frac{7.73}{3.1}\) or 1 : 25 or 2 : 5

The formula of the second oxide is X₂O₂.

Question 4. Calculate the mass of 0.2 moles of water (O = 16, H = 1).
Answer.

Given:

Gram molecular weight of H₂O = 2 × 1 + 16 = 18 g

1 mole of water weighs 18 g

Therefore, 0.2 moles of water weighs \(\frac{18}{1}\) × 0.2 = 3.6 g

Question 5. Calculate the volume of 7.1 g of chlorine (Cl = 35.5) at S.T.P.
Answer.

Given:

Gram Molecular Weight of Cl₂ (one mole) = 35.5 × 2 = 71 g.

71 g of Cl₂ at S.T.P occupies 22.4 litres

Therefore, 7.1 g of Cl₂ at S.T.P occupies

⇒ \(\frac{22.4}{71} \times 7.1=2.24 \text { litres }\)

Question 6. The reaction between aluminium carbide and water takes place according to the following equation:

Al₄C₃ + 12H₂O → 3CH₄ + 4Al(OH)₃

Calculate the volume of CH4 released from 14.4 g of Al₄C₃ by excess water at S.T.P. (C = 12, Al = 27)
Answer.

Given

CH4 released from 14.4 g of Al₄C₃ by excess water at S.T.P. (C = 12, Al = 27)

Molecular weight of Al₄C₃ is (27 × 4) + (12 × 3) = 144

144 g of Al₄C₃ produces 3 × 22.4 litres of CH₄ at S.T.P

Therefore, 14.4 g Al₄C₃ produces \(\frac{3 \times 22.4}{144} \times\) 14.4

⇒ \(=\frac{967.7}{144}=6.72 \text { litres }\)

Question 7. How many litres of ammonia are present in 3.4 kg of it? (N = 14, H = 1)
Answer.

Given:

Gram molecular weight of NH₃ = 14 + (1 × 3) = 17 g.

17 g of NH₃ = 22.4 litres

Therefore, 3.4 × 103g of NH₃ = \(\frac{22.4}{17} \times 3.4 \times 10^3\)

= \(\frac{76160}{17}\)

= 4480 litres.

Question 8. Define a mole.
Answer.

Mole: A mole is the amount of substance that contains as many elementary entities as there are atoms in 12 grams in carbon 12 isotopes .

Question 2. Find out the molar mass of sulphuric acid.
Answer.

Formula of sulphuric acid = H₂SO₄

No. of atoms:

H = 2

S = 1

O = 4

Atomic mass:

H = 1

S = 32

O = 16

Molar mass= (2 × 1) + (1 × 32) + (4 × 16) = 98 g/mol

Question 9. Calculate the number of moles and atoms in 240 grams of O (Oxygen) atom.
Answer.

Atomic Mass of O = 16 u

16 u of O = 1 atom of oxygen

16 g of O = 1 mole of oxygen

16 g of O = 6.022 × 10²³ atom of O

240 g of O = 15 moles of O

240 g of O = 15 × 6.022 × 10²³ atoms

Therefore, 240 g of O = 90.33 × 10²³ atoms.

Question 10. Find out the weight of 120.44 × 10²³ molecules of water.
Answer.

Molecular mass of H₂O = 18 u [(1 × 2) H + (16 × 1)O]

So, 1 mole = 18 g H₂O

6.022 × 10²³ = 18 g

120.44 × 10²³ = (120.44 × 10²³/6.022 × 10²³) × 18

= 20 × 18 = 360 g

Question 11. 6.6 g of CaCO₃on heating gave 2.98 g CaO and 3.62 g CO₂. Prove that these observations agree with law of conservation of mass.
Answer.

Given:

6.6 g of CaCO₃on heating gave 2.98 g CaO and 3.62 g CO₂.

CaCO₃ → CaO + CO₂

6.6g → 2.88 g + 3.52 g

Mass of the reactant = 6.4 g

Mass of the product = (2.98 + 3.62) g = 6.6 g

These results agree with the law of conservation of mass as the mass of reactants is equal to the mass of products.

Question 12. An 80.0 g sample of an unknown compound contains 16.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?
Answer.

Given:

An 80.0 g sample of an unknown compound contains 16.4 g of hydrogen.

Mass of the compound = 80 g

Mass of hydrogen in the compound = 16.4 g

Therefore, the mass fraction of hydrogen in the unknown compound = (16.4/80) x 100% = 20.5%

Question 13. What is the importance of law of conservation of mass in everyday life?
Answer.

Importance of law of conservation of mass in everyday life: Law of conservation of mass is important to study to produce chemical reactions. Chemists can predict the amount of products that will be produced in a chemical reaction if they know the amount and identities of the reactants.

Question 14. What is the limitation of law of definite proportions?
Answer.

Limitation of law of definite proportions: The law of definite proportions does not hold good for those elements who are also present in different isotopic forms in a compound.

Chemistry Multiple Choice Question And Answers

Question 1. Air is a/an

1. element
2. compound
3. mixture
4. colloid

Answer. 3. mixture

Question 2. All the following are examples of chemical change, except

1. magnetising of iron nail
2. rusting of iron rod
3. digestion of food
4. souring of milk

Answer. 1. magnetising of iron nail

Question 3. Atomic number of an element gives

1. the number of electrons in its atom
2. the number of nucleons in its atom
3. the weight of the atom of the element
4. the total number of elementary particles in its atom

Answer. 1. the number of electrons in its atom

Question 4. Conversion of a substance directly from solid to vapour state is known as

1. vapourization
2. sublimation
3. decomposition
4. ionization

Answer. 3. decomposition

Question 5. Cooking oil can be converted into vegetable ghee by the process of

1. hydrogenation
2. distillation
3. crystallization
4. oxidation

Answer. 4. oxidation

Question 6. Colloids

1. are true solutions
2. are suspensions of one phase in another
3. are two-phase systems
4. contain only water soluble substances

Answer. 2. are suspensions of one phase in another

Question 7. Colloids are purified by

1. peptization
2. coagulation
3. condensation
4. dialysis

Answer. 1. peptization

Question 8. Distillation at reduced pressure is used for liquids which have

1. high boiling points
2. low boiling points
3. high volatility
4. decomposed before their boiling points

Answer. 4. decomposed before their boiling points

Question 9. Gases have

1. a definite shape but not volume
2. a definite volume and shape
3. a definite volume but not shape
4. neither definite volume nor shape

Answer. 4. neither definite volume nor shape

Question 10. Isotopes of an element

1. are physically identical with each other
2. are chemically identical with each other
3. are not identical with each other
4. have the same mass numbers

Answer. 2. are chemically identical with each other

Question 11. Milk is an example of

1. sol
2. gel
3. emulsion
4. suspension

Answer. 3. emulsion

Question 12. Of all the gases present in the air, which one of the following is the highest in percentage?

1. Carbon dioxide
2. Hydrogen
3. Nitrogen
4. Oxygen

Answer. 3. Nitrogen

Question 13. Of the following particles, the particle having the least mass is

1. meson
2. neutron
3. electron
4. proton

Answer. 3. electron

Question 14. The atomic weight of uranium is

1. 237
2. 238
3. 226
4. 242

Answer. 2. 238

Question 15. The charge on the electron is

1. 1.6 × 10^-16 C
2. 1.5 × 10^-16 C
3. –1.6 × 10^-19 C
4. 1.6 × 10¹⁹ C

Answer. 3. –1.6 × 10^-19 C

Question 16. The chemical name of table salt is

1. potassium chloride
2. sodium chloride
3. calcium chloride
4. sodium hyposulphate

Answer. 2. sodium chloride

Question 17. The difference between isotopes of an element is due to the presence of a different number of

1. protons
2. neutrons
3. electrons
4. photons

Answer. 2. neutrons

Question 18. The ejection of electrons when a metal surface is irradiated is called

1. black body radiation
2. photoelectric effect
3. zeeman effect
4. atomic spectrum

Answer. 2. photoelectric effect

Question 19. The major constituent of air is

1. nitrogen
2. carbon dioxide
3. oxygen
4. hydrogen

Answer. 1. nitrogen

Question 20. The mass number of a nucleus is

1. always less than its atomic number
2. the sum of the number of protons and neutrons present in the nucleus
3. always more than the atomic weight
4. a fraction

Answer. 2. the sum of the number of protons and neutrons present in the nucleus

Question 21. The mass of one Avogadro number of helium atom is

1. 1.00 g
2. 4.00 g
3. 8.00 g
4. 4 × 6.02 × 1023 g

Answer. 3. 8.00 g

Question 22. The maximum capacity of any orbital is

1. 2
2. 6
3. 14
4. Cannot be determined unless the principal quantum number is known

Answer. 2. 6

Question 23. The melting point of copper is

1. 1,083°C
2. 732°C
3. 327°C
4. 1,835°C

Answer. 1. 1,083°C

Question 24. The most abundant rare gas in the atmosphere is

1. He
2. Ne
3. Ar
4. Xe

Answer. 3. Ar

Question 25. The nuclear particles that are assumed to hold nucleons together are

1. electrons
2. positrons
3. neutrons
4. mesons

Answer. 4. mesons

Question 26. The nucleus of a hydrogen atom consists of

1. one proton + one neutron
2. one proton + two neutrons
3. one neutron only
4. one electron only

Answer. 3. one neutron only

Question 27. Tritium has an atomic number of

1. 3
2. 2
3. 1
4. 4

Answer. 1. 3

Question 28. Which of the following has the same atomic number and atomic weight?

1. Hydrogen
2. Helium
3. Oxygen
4. Nitrogen

Answer. 2. Helium

Question 29. Which of the following is a chemical change?

1. evaporation of water
2. burning of candle
3. glowing of an electric bulb
4. liquefaction of air

Answer. 1. evaporation of water

Question 30. Which of the following is a mixture?

1. gunpowder
2. iron sulphate
3. brass
4. dry ice

Answer. 4. dry ice

Question 31. Which of the following is incorrect?

1. Mercury: Hg
2. Silver: Ag
3. Sodium: Na
4. Potassium: Ka

Answer. 2. Silver: Ag

Question 32. Which of the following is not a chemical action?

1. Burning of coal
2. Conversion of water into steam
3. Digestion of food
4. Burning of paper

Answer. 2. Conversion of water into steam

Question 33. A small quantity of a mixture of two days can be separated by

1. fractional distillation
2. paper chromatography
3. sublimation
4. steam distillation

Answer. 4. steam distillation

Question 34. Bohr model of an atom could not account for

1. emission spectrum
2. absorption spectrum
3. line spectrum of hydrogen
4. fine spectrum

Answer. 1. emission spectrum

Question 35. Camphor can easily be purified by the process of

1. sublimation
2. distillation
3. crystallization
4. sedimentation

Answer. 2. distillation

Question 36. Gunpowder is a mixture of

1. sulphur, carbon and phosphorus
2. sulphur, charcoal and nitre
3. sulphur, charcoal and carbon
4. carbon, nitrogen and chlorine

Answer. 3. sulphur, charcoal and carbon

Question 37. Match the following columns

List I                     List II

A. Mercury          1. Element

B. Oxygen           2. Compound

C. Water             3. Mixture

D. Air Codes       4. Metal

A      B     C     D

1      2      3     4

4      3      2     1

4      1      2     3

4      2      3     1

Answer. 3. 4 1 2 3

Question 38. Blue colour of the sky is due to

1. absorption of light by dust particles
2. reflection of light by dust particles
3. scattering of light by dust particles
4. the presence of clouds which are a colloidal dispersion of water particles in air

Answer. 1. absorption of light by dust particles

Question 39. If NA is Avogadro‘s number, then number of electrons in 4.2 g of azide ions (N₃^–) is

1. 2 N_A
2. 4.2 N_A
3. 1.6 N_A
4. 3.6 N_A

Answer. 2. 4.2 N_A

Question 40. The number of atoms present in 21.6 g of silver (atomic weight = 108) are same as the molecules in

1. 1.8 g of H₂O
2. 12 moles of KMnO₄
3. 0.6 N H₂SO₄
4. 4.6 g of C₂H₅OH

Answer. 1. 1.8 g of H₂O

Question 41. 19.7 kg of gold was recovered from a smuggler. how many atoms of gold were recovered?

(Au = 197)

1. 6.02 × 10²⁵
2. 6.02 × 10²⁴
3. 6.02 × 10²³
4. 6.02 × 10²²

Answer. 1. 6.02 × 10²⁵

Question 42. Butter is an example of

1. gel
2. emulsion
3. sol
4. foam

Answer. 3. sol

Question 43. An element M has an atomic number 9 and atomic mass 19. Its ion will be presented by

1. M
2. M²⁺
3. M^–
4. M^2-

Answer. 2. M²⁺

Question 44. Milk is

1. fat dispersed in milk
2. fat dispersed in water
3. water dispersed in fat
4. water dispersed in oil

Answer. 2. fat dispersed in water

Question 45. the formula of the compound is A₂B₅. The number of electrons in the outermost orbits of A and B respectively are

1. 6 and 3
2. 5 and 6
3. 5 and 2
4. 2 and 3

Answer. 4. 2 and 3

Question 46. Milk is a mixture of

1. fats and water
2. carbohydrates and water
3. carbohydrates, fats and water
4. carbohydrates, fats, proteins and water

Answer. 2. carbohydrates and water

Question 47. Swelling of a sprained foot is reduced by soaking in hot water containing a large amount of common salt. This is because of a phenomenon called

1. osmosis
2. plasmolysis
3. electrolysis
4. dialysis

Answer. 4. dialysis

Question 48. The percentage, by weight, of water in the human body is

1. 20
2. 40–45
3. 5–10
4. 70–75

Answer. 4. 70–75

Question 49. The so-called fourth state of matter refers to

1. mercury
2. LPG
3. dry ice
4. plasma

Answer. 3. dry ice

Question 50. Which of the following cannot be purified by sublimation?

1. iodine
2. camphor
3. citric acid
4. naphthalene

Answer. 2. camphor

Question 51. Which of the following gases in air unites with many metals?

1. hydrogen
2. oxygen
3. helium
4. carbon dioxide

Answer. 1. hydrogen

Question 52. Why does milk curdle?

1. fermentation of lactose
2. reaction of microbes
3. overheating
4. fungus growth

Answer. 3. overheating

Question 53. A fractionating column is a glass apparatus used to

1. separate magnetic solids from nonmagnetic solids
2. separate a mixture in water
3. separate two or more liquids
4. extract oils from vegetable matter

Answer. 1. separate magnetic solids from nonmagnetic solids

Question 54. In case of a chemical change, which of the following is generally affected?

1. electron
2. proton
3. neutron
4. nucleus

Answer. 1. electron

Question 55. In the natural ‘water cycle’, water gets purified by

1. evaporation and condenzation
2. sedimentation
3. filtration
4. distillation

Answer. 3. filtration

Question 56. Neutrons are obtained by

1. bombardment of radium with a-particles
2. bombardment of beryllium with a particles
3. radioactive disintegration of uranium
4. None of these

Answer. 2. bombardment of beryllium with a particles

Question 57. Radioactive isotope of hydrogen is

1. Hydride ion
2. Tritium
3. Protium
4. Deuterium

Answer. 3. Protium

Question 58. The British physicist who received the 1923 Nobel Prize in Physics for discovering the electron is

1. John Dalton
2. James Chadwick
3. J J Thomson
4. E Rutherford

Answer. 2. James Chadwick

Question 59. The number of electrons present in H+ is

1. zero
2. one
3. two
4. three

Answer. 3. two

Question 60. The smallest particle of a pure substance showing all the properties is

1. always an atom
2. always a molecule
3. may be an atom or a molecule
4. a proton

Answer. 2. always a molecule

Question 61. The total energy of an electron revolving round the nucleus is

1. less than zero
2. zero
3. more than zero
4. more than zero in some atoms and less than zero in other atoms

Answer. 1. less than zero

Question 62. When hydrogen nuclei trap neutrons, they become

1. hydrogen atoms
2. deuterons
3. tritium atom
4. beta rays

Answer. 2. deuterons

Question 63. Which of the following statements concerning an electron is false?

1. It is a particle
2. It has wave properties
3. Its path is bent by a magnet
4. It gives out energy while moving in orbit

Answer. 4. It gives out energy while moving in orbit

Question 64. Which of the following statements is true?

1. The ‘free’ electron outside the atom can have only discrete energy, in accordance with the quantum theory
2. The electron inside the atom can have a continuous range of energies
3. The kinetic energy of a free electron outside the atom can have any value in a continuous range
4. None of these

Answer. 3. The kinetic energy of a free electron outside the atom can have any value in a continuous range

Question 65. _________is the simplest form of matter.

1. Liquid
2. Solid
3. Gas
4. Plasma

Answer. 3. Gas

Question 66. A solution can be

1. Dilute and concentrated
2. Saturated and dilute
3. Saturated and unsaturated
4. Supersaturated and saturated

Answer. 2. Saturated and dilute

Question 67. Alpha rays are actually

1. 1 protons 2 neutrons
2. 2 protons 2 electrons
3. 2 protons 2 neutrons
4. 2 protons 1 neutrons

Answer. 3. 2 protons 2 neutrons

Question 68. Atomic weight of Ca is

1. 20
2. 40
3. 45
4. 80

Answer. 2. 40