CBSE Class 9 Science The Fundamental Unit of Life Sure Shot Questions Set 03

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ASSIGNMENT QUESTIONS SET - 3
CHAPTER - 5
THE FUNDAMENTAL UNIT OF LIFE

1. Which of the following can be made into crystal? [1 Mark]
(a) A Bacterium
(b) An Amoeba
(c) A Virus
(d) A Sperm

Answer: (c) A Virus

1. Viruses are unique infectious agents that lack cellular machinery on their own.
2. They can be crystallized outside a host cell, a property discovered by W.M. Stanley for Tobacco Mosaic Virus.
3. Hence, the correct option is (c).

Teacher's Note:
a) Viruses exist on the borderline of living and non-living.
b) Crystallization of viruses helps in studying their structural biology.
c) Bacteria and amoebae are complete cells and cannot be crystallized.

2. A cell will swell up if [1 Mark]
(a) The concentration of water molecules in the cell is higher than the concentration of water molecules in surrounding medium
(b) The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell
(c) The concentration of water molecules is same in the cell and in the surrounding medium
(d) Concentration of water molecules does not matter

Answer: (b) The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell

1. A cell swells when water enters it through endosmosis.
2. Endosmosis occurs when the surrounding medium is hypotonic, meaning it has a higher water concentration than the cell interior.
3. Hence, the correct option is (b).

Teacher's Note:
a) Water moves from a region of higher water concentration to lower concentration across a semipermeable membrane.
b) Hypotonic solutions cause animal cells to burst and plant cells to become turgid.
c) Hypertonic solutions lead to shrinkage or plasmolysis of cells.

3. Chromosomes are made up of [1 Mark]
(a) DNA
(b) protein
(c) DNA and protein
(d) RNA

Answer: (c) DNA and protein

1. Chromosomes are composed of deoxyribonucleic acid (DNA) and proteins (histones).
2. DNA stores hereditary information, while proteins provide structural support and help regulate gene expression.
3. Hence, the correct option is (c).

Teacher's Note:
a) Chromatin material gets organized into visible chromosomes during cell division.
b) Do not confuse chromosomes with pure DNA molecules alone.
c) Histone proteins package the very long DNA molecules compactly into the nucleus.

4. Which of these options are not a function of Ribosomes? [1 Mark]
(i) It helps in manufacture of protein molecules
(ii) It helps in manufacture of enzymes
(iii) It helps in manufacture of hormones
(iv) It helps in manufacture of starch molecules
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (iv) and (i)

Answer: (c) (iii) and (iv)

1. Ribosomes are the sites of protein synthesis (and enzymes, which are proteinaceous in nature).
2. Ribosomes do not synthesize hormones (some hormones are peptide-based, but synthesis involves broader cellular machinery including ER and Golgi) or starch molecules.
3. Hence, statements (iii) and (iv) are not functions of ribosomes, making option (c) correct.

Teacher's Note:
a) Starch is a carbohydrate manufactured by plastids (chloroplasts) in plants.
b) Read multiple statement questions carefully to eliminate correct functions first.
c) Ribosomes are found free in the cytoplasm or attached to the rough endoplasmic reticulum.

5. Which of these is not related to endoplasmic reticulum? [1 Mark]
(a) It behaves as transport channel for proteins between nucleus and cytoplasm
(b) It transports materials between various regions in cytoplasm
(c) It can be the site of energy generation
(d) It can be the site for some biochemical activities of the cell

Answer: (c) It can be the site of energy generation

1. Mitochondria are the sites of cellular respiration and energy generation (ATP synthesis), not the endoplasmic reticulum.
2. The endoplasmic reticulum acts as a transport channel, lipid/protein synthesizer, and site for biochemical activities.
3. Hence, the correct option is (c).

Teacher's Note:
a) Energy currency of the cell is ATP, produced in mitochondria.
b) Endoplasmic reticulum exists as a network of membrane-bound tubules and sheets.
c) Smooth ER helps in lipid synthesis, while rough ER helps in protein synthesis.

6. Following are a few definitions of osmosis. Read carefully and select the correct definition [1 Mark]
(a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane
(b) Movement of solvent molecules from its higher concentration to lower concentration
(c) Movement of solvent molecules from higher concentration to lower concentration of solution through a permeable membrane
(d) Movement of solute molecules from lower concentration to higher concentration of solution through a semipermeable membrane

Answer: (a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane

1. Osmosis is the passage of water from a region of high water concentration through a semipermeable membrane to a region of low water concentration.
2. It is a special case of diffusion through a selectively permeable membrane.
3. Hence, the correct option is (a).

Teacher's Note:
a) Osmosis strictly involves solvent or water movement across a semipermeable membrane.
b) Pay close attention to the terms solvent versus solute and permeable versus semipermeable.

7. Plasmolysis in a plant cell is defined as [1 Mark]
(a) break down (lysis ) of plasma membrane in hypotonic medium
(b) shrinkage of cytoplasm in hypertonic medium
(c) shrinkage of nucleoplasm
(d) none of them

Answer: (b) shrinkage of cytoplasm in hypertonic medium

1. When a plant cell loses water through osmosis, there is shrinkage or contraction of the contents of the cell away from the cell wall.
2. This phenomenon is known as plasmolysis, which occurs when a cell is placed in a hypertonic medium.
3. Hence, the correct option is (b).

Teacher's Note:
a) Hypertonic solutions have higher solute concentration, causing water to flow out of the cell.
b) Plasmolysis only affects living cells, demonstrating osmosis in plant tissues.

8. Which of the following are covered by a single membrane? [1 Mark]
(a) Mitochondria
(b) Vacuole
(c) Lysosome
(d) Plastid

Answer: (b) Vacuole (the marking scheme also accepts option (c) depending on standard textbook classifications where vacuoles and lysosomes are single-membraned, whereas mitochondria and plastids have double membranes; vacuoles are the classic single membrane storage structures).

1. Vacuoles are storage sacs for solid or liquid contents bound by a single membrane called tonoplast.
2. Mitochondria and plastids are double-membraned organelles.
3. Hence, the correct option is (b).

Teacher's Note:
a) Organelles can be classified by their membrane structure as single, double, or non-membraned.
b) Students often confuse single membrane structures like lysosomes and vacuoles with double-membraned powerhouses.

9. Find out the false sentences [1 Mark]
(a) Golgi apparatus is involved with the formation of lysosomes
(b) Nucleus, mitochondria and plastid have DNA; hence they are able to make their own structural proteins
(c) Mitochondria is said to be the power house of the cell as ATP is generated in them.
(d) Cytoplasm is called as protoplasm

Answer: (d) Cytoplasm is called as protoplasm

1. Protoplasm includes both the cytoplasm and the nucleoplasm, making cytoplasm only a part of protoplasm.
2. Statements (a), (b), and (c) are scientifically correct facts about cell organelles.
3. Hence, option (d) is the false statement.

Teacher's Note:
a) Protoplasm is the entire living substance of a cell, encompassing the nucleus and cytoplasm.
b) Read every option carefully in 'find the false statement' type questions to avoid missing subtle distinctions.

10. Find out the correct sentence [1 Mark]
(a) Enzymes packed in Lysosomes are made through RER (rough endoplasmic reticulum)
(b) Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein respectively
(c) Endoplasmic reticulum is related with the destruction of plasma membrane
(d) Nucleoid is present inside the nucleoplasm of eukaryotic nucleus

Answer: (a) Enzymes packed in Lysosomes are made through RER (rough endoplasmic reticulum)

1. RER has ribosomes on its surface which synthesize proteins, including digestive enzymes later packaged into lysosomes.
2. SER produces lipids, while RER produces proteins, reversing statement (b).
3. Hence, the correct option is (a).

Teacher's Note:
a) Structure and function of Rough versus Smooth Endoplasmic Reticulum are frequently tested concepts.
b) Ribosomes attached to RER manufacture proteins which are fundamental for cellular enzymatic functions.

11. Which cell organelle plays a crucial role in detoxifying many poisons and drugs in a cell? [1 Mark]
(a) Golgi apparatus
(b) Lysosomes
(c) Smooth endoplasmic reticulum
(d) Vacuoles

Answer: (c) Smooth endoplasmic reticulum

1. Smooth Endoplasmic Reticulum (SER) plays a crucial role in detoxifying many poisons and drugs in the liver cells of vertebrates.
2. It lacks ribosomes on its surface, giving it a smooth appearance.
3. Hence, the correct option is (c).

Teacher's Note:
a) SER is specialized for lipid synthesis and detoxification processes.
b) Connect this function directly with liver cells to remember SER roles easily.

12. The proteins and lipids, essential for building the cell membrane, are manufactured by [1 Mark]
(a) rough endoplasmic reticulum
(b) golgi apparatus
(c) plasma membrane
(d) mitochondria

Answer: (a) rough endoplasmic reticulum

1. Rough endoplasmic reticulum has ribosomes attached to its surface which manufacture proteins.
2. Smooth endoplasmic reticulum helps in the manufacture of fat molecules or lipids.
3. These proteins and lipids are essential for building the cell membrane, a process known as membrane biogenesis.
4. Hence, the correct option is (a).

Teacher's Note:
a) Rough endoplasmic reticulum (RER) appears rough under a microscope because of the presence of ribosomes.
b) Do not confuse RER with smooth endoplasmic reticulum, which synthesizes lipids rather than proteins.
c) Membrane biogenesis relies heavily on the combined output of both types of endoplasmic reticulum.

13. The undefined nuclear region of prokaryotes are also known as [1 Mark]
(a) nucleus
(b) nucleolus
(c) nucleic acid
(d) nucleoid

Answer: (d) nucleoid

1. Prokaryotic cells lack a defined nuclear membrane, so their genetic material is just a nucleic acid without an envelope.
2. This undefined nuclear region containing only nucleic acid is called a nucleoid.
3. Hence, the correct option is (d).

Teacher's Note:
a) Prokaryotes lack membrane-bound organelle structures, including a true nuclear membrane.
b) A nucleoid contains the single circular DNA molecule typical of bacteria and other prokaryotic organisms.
c) Eukaryotes possess a true nucleus bounded by a double membrane.

14. The cell organelle involved in forming complex sugars from simple sugars are [1 Mark]
(a) endoplasmic reticulum
(b) ribosomes
(c) plastids
(d) golgi apparatus

Answer: (d) golgi apparatus

1. The materials synthesized near the endoplasmic reticulum are packaged and dispatched to various targets by the golgi apparatus.
2. Its functions include the storage, modification, and packaging of products in vesicles.
3. Complex sugars may be formed from simple sugars in the golgi apparatus.
4. Hence, the correct option is (d).

Teacher's Note:
a) Camillo Golgi first described the golgi apparatus, which consists of a system of membrane-bound vesicles.
b) It is also involved in the formation of lysosomes in many cells.
c) Students often confuse the manufacturing site (ER) with the modification and packaging site (golgi apparatus).

15. Which out of the following is not a function of vacuole? [1 Mark]
(a) Storage
(b) Providing turgidity and rigidity to the cell
(c) Waste excretion
(d) Locomotion

Answer: (d) Locomotion

1. Vacuoles are storage sacs for solid or liquid contents.
2. In plant cells, central vacuoles are full of cell sap and provide turgidity and rigidity.
3. They also play an important role in expelling excess water and wastes from the cell in some organisms, but they are not involved in locomotion.
4. Hence, the correct option is (d).

Teacher's Note:
a) Locomotion in single-celled organisms is typically carried out by structures like cilia or flagella, not vacuoles.
b) Plant vacuoles can occupy up to ninety percent of the volume of the cell.
c) Amoeba utilizes food vacuoles for nutrition, but contractile vacuoles for osmoregulation.

16. Amoeba acquires its food through a process, termed [1 Mark]
(a) exocytosis
(b) endocytosis
(c) plasmolysis
(d) exocytosis and endocytosis both

Answer: (b) endocytosis

1. The flexibility of the cell membrane enables the cell to engulf food and other material from its external environment.
2. Such processes are known as endocytosis.
3. Amoeba acquires its food through this flexible membrane engulfment.
4. Hence, the correct option is (b).

Teacher's Note:
a) Endocytosis is a cellular process in which substances are brought into the cell.
b) Exocytosis is the reverse process of expelling material out of the cell.
c) Plasmolysis refers to the shrinkage of plant cells due to water loss in a hypertonic medium.

17. Cell wall of which one of these is not made up of cellulose? [1 Mark]
(a) Bacteria
(b) Hydrilla
(c) Mango tree
(d) Cactus

Answer: (a) Bacteria

1. Plant cells like Hydrilla, mango trees, and cacti have cell walls primarily composed of cellulose.
2. Bacteria are prokaryotes whose cell walls are made up of peptidoglycan, not cellulose.
3. Hence, the correct option is (a).

Teacher's Note:
a) Cellulose is a complex substance and provides structural strength to plant cells.
b) Bacterial cell walls have a distinctly different chemical composition from plant cell walls.
c) Fungi have cell walls made of chitin, serving as another exception to plant cellulose walls.

18. Silver nitrate solution is used to study [1 Mark]
(a) endoplasmic reticulum
(b) golgi apparatus
(c) nucleus
(d) mitochondria

Answer: (b) golgi apparatus

1. Camillo Golgi stained the golgi apparatus using a fast impregnation method with silver nitrate.
2. This silver staining technique enabled the microscopic visualization of the intricate reticular structure of the golgi apparatus.
3. Hence, the correct option is (b).

Teacher's Note:
a) Camillo Golgi received the Nobel Prize in 1906 for his work on the nervous system and staining techniques.
b) Silver nitrate impregnation is a classic cytological staining method.
c) Other cell organelles require different specific stains, like iodine for starch or methylene blue for nuclei.

19. Organelle other than nucleus, containing DNA is [1 Mark]
(A) endoplasmic reticulum
(B) golgi apparatus
(C) mitochondria
(D) lysosome

Answer: (C) mitochondria

1. Mitochondria and plastids are unique organelles that possess their own circular DNA and ribosomes.
2. This allows them to make some of their own proteins independently.
3. Hence, the correct option is (C).

Teacher's Note:
a) Mitochondria contain their own DNA.
b) They are known as the powerhouse of the cell.
c) Remember that chloroplasts also contain DNA.

20. Kitchen of the cell is [1 Mark]
(A) mitochondria
(B) endoplasmic reticulum
(C) chloroplast
(D) golgi apparatus

Answer: (C) chloroplast

1. Chloroplasts contain the green pigment chlorophyll and are the site of photosynthesis in plant cells.
2. Since food is prepared inside them through photosynthesis, they are called the kitchen of the cell.
3. Hence, the correct option is (C).

Teacher's Note:
a) Chloroplasts perform photosynthesis.
b) Do not confuse with mitochondria which are powerhouses.
c) They are found exclusively in plant cells and some protists.

21. Lipid molecules in the cell are sythesized by [1 Mark]
(A) smooth endoplasmic reticulum
(B) rough endoplasmic reticulum
(C) golgi apparatus
(D) plastids

Answer: (A) smooth endoplasmic reticulum

1. Smooth Endoplasmic Reticulum (SER) lacks ribosomes on its surface, giving it a smooth appearance.
2. It plays a crucial role in the synthesis of lipids, cellular-membrane building blocks, and steroids.
3. Hence, the correct option is (A).

Teacher's Note:
a) SER synthesizes lipids.
b) RER synthesizes proteins due to attached ribosomes.
c) Note the spelling typo in the question paper sythesized.

22. Cell arises from pre-existing cell was stated by [1 Mark]
(A) Haeckel
(B) Virchow
(C) Hooke
(D) Schleiden

Answer: (B) Virchow

1. Rudolf Virchow in 1855 expanded the cell theory by suggesting that all cells arise from pre-existing cells (Omnis cellula-e cellula).
2. This formed the third major tenet of modern cell theory.
3. Hence, the correct option is (B).

Teacher's Note:
a) Virchow proposed omnis cellula-e cellula.
b) Hooke discovered cells in cork.
c) Schleiden and Schwann proposed the initial cell theory.

23. Cell theory was given by [1 Mark]
(A) Schleiden and Schwann
(B) Virchow
(C) Hooke
(D) Haeckel

Answer: (A) Schleiden and Schwann

1. Matthias Schleiden and Theodor Schwann formulated the basic cell theory.
2. They stated that all plants and animals are composed of cells and that the cell is the basic unit of life.
3. Hence, the correct option is (A).

Teacher's Note:
a) Schleiden and Schwann founded cell theory.
b) Virchow later added to it.
c) A foundational concept in biology.

24. The only cell organelle seen in prokaryotic cell is [1 Mark]
(A) mitochondria
(B) ribosomes
(C) plastids
(D) lysosomes

Answer: (B) ribosomes

1. Prokaryotic cells lack membrane-bound organelles like mitochondria, plastids, and lysosomes.
2. Ribosomes are non-membrane-bound organelles present in both prokaryotes and eukaryotes.
3. Hence, the correct option is (B).

Teacher's Note:
a) Ribosomes lack a surrounding lipid membrane.
b) Prokaryotes have 70S type ribosomes.
c) Membrane-bound organelles are absent in prokaryotes.

25. Organelle without a cell membrane is [1 Mark]
(A) ribosome
(B) golgi apparatus
(C) chloroplast
(D) nucleus

Answer: (A) ribosome

1. Ribosomes are composed of RNA and proteins and are not enclosed by any membrane.
2. Golgi apparatus, chloroplast, and nucleus are all bound by double or single membranes.
3. Hence, the correct option is (A).

Teacher's Note:
a) Ribosomes are non-membranous structures.
b) They are found in the cytoplasm and attached to the rough endoplasmic reticulum.
c) Essential for protein synthesis in all living cells.

26. 1 µm is [1 Mark]
(A) 10^-6 m
(B) 10^-9 m
(C) 10^-10 m
(D) 10^-3 m

Answer: (A) 10^-6 m

1. Micrometre is denoted by µm.
2. One micrometre is equal to 10^-6 metres.
3. Hence, the correct option is (A).

Teacher's Note:
a) Remember standard metric prefixes for cell biology conversions.
b) 1 nanometre equals 10^-9 m.

27. Lysosome arises from [1 Mark]
(A) endoplasmic reticulum
(B) golgi apparatus
(C) nucleus
(D) mitochondria

Answer: (B) golgi apparatus

1. Lysosomes are membrane-bound vesicles formed by the process of packaging in the golgi apparatus.
2. Digestive enzymes contained in lysosomes are synthesized by rough endoplasmic reticulum and transported to golgi apparatus.
3. Hence, the correct option is (B).

Teacher's Note:
a) Connect the synthesis site of enzymes with their packaging organelle.
b) Do not confuse the site of protein synthesis with the site of vesicle formation.

28. Living cells were discovered by [1 Mark]
(A) Robert Hooke
(B) Purkinje
(C) Leeuwenhoek
(D) Robert Brown

Answer: (C) Leeuwenhoek

1. Robert Hooke discovered dead cells in cork slices.
2. Anton van Leeuwenhoek first observed living cells like bacteria and protozoa using an improved microscope.
3. Hence, the correct option is (C).

Teacher's Note:
a) A classic distinction exists between Hooke's dead cork cells and Leeuwenhoek's living cells.
b) Students often mistakenly credit Robert Hooke for discovering living cells.

29. Select the odd one out [1 Mark]
(A) The movement of water across a semi permeable membrane is affected by the amount of substances dissolved in it.
(B) Membranes are made of organic molecules like proteins and lipids
(C) Molecules soluble in organic solvents can easily pass through the membrane.
(D) Plasma membranes contain chitin sugar in plants

Answer: (D) Plasma membranes contain chitin sugar in plants

1. Plant cell walls contain cellulose, not chitin, and plasma membranes are composed of lipids and proteins.
2. Chitin is found in the cell walls of fungi and arthropod exoskeletons.
3. Statements (A), (B), and (C) state correct biological facts regarding cell membranes.
4. Hence, the correct option is (D).

Teacher's Note:
a) Analyze plant cell wall components versus plasma membrane composition.
b) Chitin is a complex carbohydrate found in fungi, not plant plasma membranes.

30. Why are lysosomes known as 'suicide-bags' of a cell? [2 Marks]

Answer:
1. Lysosomes contain powerful digestive enzymes capable of breaking down all organic material.
2. When the cell gets damaged or disturbed, lysosomes may burst, and the enzymes digest their own cell, hence they are called suicide bags.

Teacher's Note:
a) Mention the presence of hydrolytic enzymes.
b) Explain cellular lysis during metabolic disturbance.

31. Do you agree that "A cell is a building unit of an organism". If yes, explain why? [3 Marks]

Answer:
1. Yes, a cell is the fundamental structural and functional unit of all living organisms.
2. Just like bricks are assembled to make a building, cells are assembled to form the body of every organism.
3. All life processes, such as respiration, digestion, and excretion, occur at the cellular level.

Teacher's Note:
a) State the structural and functional role of cells clearly.
b) Use the standard brick-and-building analogy to explain structural organization.
c) Emphasize that all life activities stem from cellular functions.

32. Why does the skin of your finger shrink when you wash clothes for a long time? [2 Marks]

Answer:
1. Soap water and detergent solutions are hypertonic compared to the fluid inside our skin cells.
2. Water moves out of the skin cells into the surrounding water through osmosis, causing the skin to shrink and wrinkle.

Teacher's Note:
a) Apply the concept of hypertonic solutions and exosmosis.
b) Note that water moves from a region of higher concentration inside cells to lower concentration outside.

33. Why is endocytosis found in animals only? [2 Marks]

Answer:
1. Animal cells lack a rigid cell wall and possess a flexible plasma membrane that allows engulfing of food and other materials.
2. Plant cells have a rigid outer cell wall that prevents the flexibility required for inward engulfment of bulk material via endocytosis.

Teacher's Note:
a) Highlight the presence of the rigid cell wall in plants.
b) Contrast the flexible plasma membrane of animal cells.

34. A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain. [3 Marks]

Answer:
1. The phenomenon responsible is exosmosis.
2. A concentrated salt solution is hypertonic to the fluids inside the cells of the alimentary canal.
3. Water moves out of the cells into the stomach cavity by osmosis, causing irritation and triggering vomiting to expel the hypertonic solution.

Teacher's Note:
a) Identify exosmosis as the primary physical process.
b) Explain the tonicity gradient between the salt solution and cellular fluid.
c) Connect cellular water loss to the body's reflex reaction.

35. Name any cell organelle which is non membranous. [1 Mark]

Answer:
Ribosome (or Centrosome).

Teacher's Note:
a) Ribosomes are composed of RNA and proteins without a surrounding lipid membrane.

36. We eat food composed of all the nutrients like carbohydrates, proteins, fats, vitamins, minerals and water. After digestion, these are absorbed in the form of glucose, aminoacids, fatty acids, glycerol etc. What mechanisms are involved in absorption of digested food and water? [3 Marks]

Answer:
1. Simple diffusion allows small molecules and certain ions to move across cell membranes along their concentration gradient.
2. Facilitated diffusion and active transport move specific molecules like glucose and amino acids across membranes with or against concentration gradients using energy.
3. Water is absorbed passively across the intestinal lining primarily through osmosis.

Teacher's Note:
a) List active transport, diffusion, and osmosis as core transport mechanisms.
b) Distinguish between passive and active movement of digested nutrients.
c) Emphasize that water moves strictly via osmotic gradients.

37. If you are provided with some vegetables to cook. You generally add salt into the vegetables during cooking process. After adding salt, vegetables release water. What mechanism is responsible for this? [2 Marks]

Answer:
1. Adding salt creates a hypertonic external medium outside the plant cells.
2. Water inside the plant cells moves out into the salted surrounding medium through the process of exosmosis.

Teacher's Note:
a) Explain tonicity changes caused by adding dry salt.
b) Emphasize exosmosis across plant cell membranes.

38. If cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? Explain the reason for your answer. [1 Mark]
(a) Both the cells will swell.
(b) RBC will burst easily while cells of onion peel will resist the bursting to some extent.
(c) a and b both are correct.
(d) RBC and onion peel cells will behave similarly.

Answer: (b) RBC will burst easily while cells of onion peel will resist the bursting to some extent.

1. In a hypotonic solution, water enters both cells due to osmosis.
2. Plant cells like onion peel have a rigid cell wall that resists bursting.
3. Animal cells like RBC lack a cell wall and burst when excess water enters.
4. Hence, the correct option is (b).

Teacher's Note:
a) Hypotonic solutions have lower solute concentration than the cell cytoplasm.
b) The cell wall exerts turgor pressure against incoming water, preventing plant cells from bursting.
c) Always remember that animal cells lyse in hypotonic media while plant cells become turgid.

39. Bacteria do not have chloroplast but some bacteria are photoautorophic in nature and perform photosynthesis. Which part of bacterial cell performs this? [1 Mark]

Answer:
1. Photosynthesis in photoautotrophic bacteria is performed by chlorophyll associated with membranous vesicles or chromatophores.
2. These are infoldings of the plasma membrane.

Teacher's Note:
a) Bacteria are prokaryotes and lack membrane-bound organelles like chloroplasts.
b) Plasma membrane extensions carry out metabolic functions equivalent to eukaryotic organelles.

40. Match the following A and B [1 Mark]

Answer:
1. (a) - (iv)
2. (b) - (v)
3. (c) - (iii)
4. (d) - (i)
5. (e) - (ii)

Teacher's Note:
a) Match each organelle with its precise cellular function or occurrence.
b) Smooth endoplasmic reticulum plays a key role in detoxifying poisons and drugs.

41. Write the name of different plant parts in which chromoplast, chloroplast and leucoplast are present. [1 Mark]

Answer:
1. Chromoplast: Present in petals of flowers and ripening fruits.
2. Chloroplast: Present in green leaves and green stems of plants.
3. Leucoplast: Present in underground parts like roots, tubers and rhizomes.

Teacher's Note:
a) Plastids are classified based on the pigments they contain.
b) Chromoplasts provide color, chloroplasts perform photosynthesis, and leucoplasts store nutrients.

42. Name the organelles which show the analogy written as under [1 Mark]
(a) Transporting channels of the cell - -
(b) Power house of the cell - -
(c) Packaging and dispatching unit of the cell - -
(d) Digestive bag of the cell - -
(e) Storage sacs of the cell - -
(f) Kitchen of the cell - -
(g) Control room of the cell - -

Answer:
1. (a) Endoplasmic Reticulum
2. (b) Mitochondria
3. (c) Golgi apparatus
4. (d) Lysosome
5. (e) Vacuole
6. (f) Chloroplast
7. (g) Nucleus

Teacher's Note:
a) Cellular analogies help map organelle functions to macroscopic systems.
b) Mitochondria are termed powerhouses because they synthesize ATP molecules.

43. How is a bacterial cell different from an onion peel cell? [2 Marks]

Answer:
1. A bacterial cell is a prokaryotic cell lacking a well-defined nuclear membrane, whereas an onion peel cell is a eukaryotic cell with a true membrane-bound nucleus.
2. Membrane-bound cell organelles like mitochondria, chloroplasts, and Golgi apparatus are absent in bacteria but present in onion peel cells.

Teacher's Note:
a) Prokaryotes have a naked nucleoid instead of a true nucleus.
b) Eukaryotes possess complex internal compartmentalization.

44. How do substances like carbon dioxide (CO₂) and water (H₂O) move in and out of the cell? [2 Marks]

Answer:
1. Carbon dioxide moves in and out of the cell by the process of diffusion, moving from a region of higher concentration to a region of lower concentration.
2. Water moves across the cell membrane by osmosis, which is the diffusion of water through a selectively permeable membrane.

Teacher's Note:
a) Diffusion is a passive transport mechanism requiring no cellular energy.
b) Osmosis is a special case of diffusion specifically involving water molecules.

45. How does amoeba obtain its food? [2 Marks]

Answer:
1. Amoeba obtains its food through a process called phagocytosis or endocytosis.
2. It extends finger-like projections of its cell surface called pseudopodia around the food particle to form a food vacuole.

Teacher's Note:
a) This form of bulk transport allows unicellular organisms to engulf solid food.
b) Digestive enzymes are secreted into the food vacuole to break down nutrients.

46. Name the two organelles in a plant cell that contain their own genetic material and ribosomes. [2 Marks]

Answer:
1. Mitochondria
2. Plastids (such as chloroplasts)

Teacher's Note:
a) These two organelles are semi-autonomous due to possessing their own DNA and ribosomes.
b) They can synthesize some of their own proteins independently.

47. Why are lysosomes also known as “scavengers of the cells”? [2 Marks]

Answer:
1. Lysosomes contain powerful digestive enzymes capable of breaking down all organic material.
2. They clean up the cell by digesting foreign materials and worn-out cell organelles, earning them the name cellular scavengers.

Teacher's Note:
a) They help in waste disposal and cellular defense.
b) During cellular damage, they may burst to digest their own cell, acting as suicide bags.

48. Which cell organelle controls most of the activities of the cell? [1 Mark]

Answer:
1. The nucleus controls most of the activities of the cell.

Teacher's Note:
a) The nucleus contains genetic material (DNA) that directs cellular metabolism and heredity.

49. Why do plant cells possess large sized vacuole? [2 Marks]

Answer:
1. Plant cells possess large vacuoles to store water, nutrients, and waste products.
2. They provide turgidity and rigidity to plant cells, helping support the structural integrity of the plant.

Teacher's Note:
a) Vacuoles can occupy up to 90 percent of the volume of a mature plant cell.
b) Turgor pressure from the central vacuole keeps plant tissues firm.

50. How are chromatin, chromatid and chromosomes related to each other? [2 Marks]

Answer:
1. Chromatin is the uncoiled, entangled network of DNA and protein threads present in a non-dividing cell.
2. During cell division, chromatin condenses into distinct chromosomes, each consisting of two identical sister chromatids joined at the centromere.

Teacher's Note:
a) Chromatin represents the working state of genetic material.
b) Chromosomes represent the compacted packaging state for safe distribution during mitosis.

51. Which kind of plastid is more common in [1 Mark]
(a) roots of the plant
(b) leaves of the plant
(c) flowers and fruits

Answer: (b) leaves of the plant

1. Chloroplasts are green-coloured plastids containing chlorophyll.
2. Leaves contain chloroplasts which are essential for photosynthesis.
3. Hence, the correct option is (b).

Teacher's Note:
a) Plastids are found only in plant cells.
b) Chromoplasts are found in flowers and fruits, while leucoplasts are common in roots.

52. What are the consequences of the following conditions? [3 Marks]
(a) A cell containing higher water concentration than the surrounding medium
(b) A cell having low water concentration than the surrounding medium.
(c) A cell having equal water concentration to its surrounding medium.

Answer:
1. (a) Water moves out of the cell by osmosis because the surrounding medium is hypertonic, causing the cell to shrink (plasmolysis).
2. (b) Water moves into the cell by osmosis because the surrounding medium is hypotonic, causing the cell to swell up or burst.
3. (c) There is no net movement of water across the cell membrane because the surrounding medium is isotonic, keeping the cell size unchanged.

Teacher's Note:
a) Osmosis is the movement of water molecules from a region of higher water concentration to a region of lower water concentration through a semi-permeable membrane.
b) Animal cells lack cell walls and may burst in hypotonic solutions, whereas plant cells have rigid cell walls to prevent bursting.
c) Always mention the direction of water flow based on tonicity gradients.

53. Draw a plant cell and label the parts which [5 Marks]
(a) determines the function and development of the cell
(b) packages materials coming from the endoplasmic reticulum
(c) provides resistance to microbes to withstand hypotonic external media without bursting
(d) is site for many biochemical reactions necessary to sustain life.
(e) is a fluid contained inside the nucleus

[Figure: Diagram of a plant cell showing nucleus, Golgi apparatus, cell wall, cytoplasm, and nucleoplasm]

Answer:
1. (a) Nucleus determines the function and development of the cell.
2. (b) Golgi apparatus packages materials coming from the endoplasmic reticulum.
3. (c) Cell wall provides resistance to microbes to withstand hypotonic external media without bursting.
4. (d) Cytoplasm is the site for many biochemical reactions necessary to sustain life.
5. (e) Nucleoplasm is a fluid contained inside the nucleus.

Teacher's Note:
a) Plant cells have distinctive structures like a rigid outer cell wall and large central vacuoles not typically found in animal cells.
b) Each organelle performs specialized metabolic roles essential for cellular survival.
c) Precise labelling of organelles ensures full credit in diagrammatic questions.
d) The nucleoplasm, also known as karyolymph, suspends chromatin and nucleoli.

54. Illustrate only a plant cell as seen under electron microscope. How is it different from animal cell? [3 Marks]

[Figure: Electron microscopic diagram of a plant cell highlighting large central vacuole, cell wall, and chloroplasts]

Answer:
1. A plant cell possesses a rigid outer cell wall made of cellulose.
2. It contains a large central vacuole that occupies a major volume of the cell.
3. Plastids such as chloroplasts are present for photosynthesis, and centrioles are typically absent.

Teacher's Note:
a) Plant cells are generally larger and more rectangular than animal cells.
b) Distinguish clearly between plant and animal cells using structural differences like vacuoles and cell walls.

c) Electron microscopy reveals ultra-structural details not visible under light microscopes.

55. Draw a neat labelled diagram of an animal cell. [3 Marks]

[Figure: Diagram of an animal cell showing plasma membrane, nucleus, mitochondria, ribosomes, and endoplasmic reticulum]

Answer:
1. The animal cell is enclosed by a flexible plasma membrane without a cell wall.
2. Key labelled parts include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and cytoplasm.
3. Small temporary vacuoles may be present scattered in the cytoplasm.

Teacher's Note:
a) Animal cells lack plastids and cell walls.
b) Diagrams must be neatly drawn with sharp pencil lines and clear arrow labels.
c) Centrioles are characteristic organelles found near the nucleus in animal cells.

56. Draw a well labelled diagram of an eukaryotic nucleus. How is it different from nucleoid? [3 Marks]

[Figure: Diagram of a eukaryotic nucleus showing nuclear membrane, nuclear pores, nucleolus, and chromatin network]

Answer:
1. A eukaryotic nucleus is well-defined and surrounded by a double-layered nuclear membrane.
2. It contains a nucleolus and distinct chromatin fibres.
3. In contrast, a nucleoid is an undefined nuclear region in prokaryotes lacking a nuclear membrane.

Teacher's Note:
a) Nuclear membrane contains pores that allow material transfer between nucleoplasm and cytoplasm.
b) Nucleoid contains only nucleic acids without surrounding histone proteins or membrane boundaries.
c) Eukaryotic DNA is organized into linear chromosomes associated with proteins.

57. Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis? [3 Marks]

Answer:
1. Rough Endoplasmic Reticulum (RER) has ribosomes attached to its surface, whereas Smooth Endoplasmic Reticulum (SER) lacks ribosomes.
2. RER is primarily responsible for protein synthesis and secretion, while SER helps in the synthesis of lipids and fats.
3. ER is important for membrane biogenesis because proteins and lipids synthesized by the ER help in building the cell membrane.

Teacher's Note:
a) Membrane biogenesis refers to the process of forming biological membranes from organic molecules.
b) Structure and function correlate directly with the presence or absence of surface ribosomes.
c) SER also plays a crucial role in detoxifying many poisons and drugs in liver cells.

58. In brief state what happens when [5 Marks]
(a) dry apricots are left for sometime in pure water and later transferred to sugar solution?
(b) a Red Blood Cell is kept in concentrated saline solution?
(c) the Plasma-membrane of a cell breaks down?
(d) rheo leaves are boiled in water first and then a drop of sugar syrup is put on it?
(e) golgi apparatus is removed from the cell?

Answer:
1. (a) Apricots swell up due to endosmosis in pure water, and then shrink due to exosmosis when placed in a concentrated sugar solution.
2. (b) The Red Blood Cell shrinks due to exosmosis as water moves out into the hypertonic saline solution.
3. (c) Cellular contents spill out, leading to cell death as the cell loses its integrity and ability to regulate internal environments.
4. (d) Plasmolysis does not occur because boiling kills the cells, destroying the semi-permeable nature of the plasma membrane.
5. (e) Storage, modification, and packaging of proteins and lipids will be disrupted, halting the formation of lysosomes and complex molecules.

Teacher's Note:
a) Osmotic movement depends strictly on the relative concentration gradients across the semi-permeable membrane.
b) Dead cells lose selective permeability, preventing osmotic reactions.
c) The plasma membrane is essential for maintaining cellular homeostasis.
d) Golgi apparatus functions as the cellular post office, modifying and dispatching products.

59. Draw a neat diagram of plant cell and label any three parts which differentiate it from animal cell. [3 Marks]

[Figure: Plant cell diagram highlighting cell wall, large central vacuole, and chloroplasts]

Answer:
1. Plant cells possess structural features distinct from animal cells.
2. Three specific parts that differentiate a plant cell from an animal cell are: Cell wall, Plastids (Chloroplasts), and Large central vacuole.

Teacher's Note:
a) Plant cells have rigid boundaries that provide mechanical support.
b) Vacuoles in plants maintain turgidity and rigidity.
c) Chloroplasts enable autotrophic nutrition via photosynthesis.

60. Draw a neat diagram of animal cell and label any three parts which differentiate it from plant cell. [3 Marks]

[Figure: Animal cell diagram highlighting centrioles, lysosomes, and small temporary vacuoles]

Answer:
1. Animal cells possess specific organelles not typically found in standard plant cells.
2. Three specific parts that differentiate an animal cell from a plant cell are: Centrioles, Lysosomes, and small temporary vacuoles.

Teacher's Note:
a) Centrioles play an active role in cell division by forming spindle fibres.
b) Lysosomes contain digestive enzymes to break down cellular waste.
c) Animal cells lack cell walls, making them flexible in shape.