Question 1. A cell is placed in a solution and after some time it becomes swollen. What can you infer about the concentration of the solution outside the cell? Explain.

Answer: The external solution is hypotonic; water enters the cell by osmosis.

Question 2. A plant cell placed in a concentrated salt solution loses water and its plasma membrane pulls away from the cell wall. What process has occurred, and why doesn’t the entire cell wall shrink?

Answer: Plasmolysis has occurred. The plasma membrane and cytoplasm lose water, while the rigid cell wall maintains its shape.

Question 3. A student observes a cell under a microscope and finds a cell wall, chloroplasts and a large vacuole. Can the student conclude that the cell must be from a leaf? Give a reasoned answer.

Answer: No. These structures are characteristic of plant cells but can also occur in other photosynthetic plant parts.

Question 4. Two cells have the same size, but ( \displaystyle \text{Cell A} ) contains many mitochondria while ( \displaystyle \text{Cell B} ) contains very few. Which cell is likely to have a higher energy demand? Why?

Answer: ( \displaystyle \text{Cell A} ), because mitochondria release energy through cellular respiration and are more numerous in cells with high energy requirements.

Question 5. A cell has a nucleus but no cell wall or chloroplast. Is it necessarily an animal cell? Explain why or why not.

Answer: No. It could be an animal cell, but some other eukaryotic cells also lack a cell wall and chloroplasts.

Question 6. A scientist removes the nucleus from a living cell. Initially, the cell continues functioning, but after some time its activities decline. What does this observation suggest about the role of the nucleus?

Answer: The nucleus controls cellular activities and contains genetic material needed for regulating cell functions.

Question 7. A cell contains numerous ribosomes but very few mitochondria. What can you infer about the type of activity occurring actively in that cell?

Answer: It is likely actively synthesising proteins, since ribosomes are involved in protein synthesis.

Question 8. A factory has a security gate, power station, production units, waste-disposal system and control room. If the cell is compared with this factory, which cell organelles would correspond to these structures?

Answer: Security gate ( \displaystyle \rightarrow ) plasma membrane; power station ( \displaystyle \rightarrow ) mitochondria; production units ( \displaystyle \rightarrow ) ribosomes/endoplasmic reticulum; waste disposal ( \displaystyle \rightarrow ) lysosomes; control room ( \displaystyle \rightarrow ) nucleus.

Question 9. A student says, “The plasma membrane is just a covering around the cell, so damaging it should not seriously affect the cell.” Do you agree? Give a reason.

Answer: No. The plasma membrane regulates movement of substances into and out of the cell and helps maintain the cell’s internal environment.

Question 10. Why would a cell with a very large surface area compared with its volume generally exchange materials more efficiently than a cell with a small surface-area-to-volume ratio?

Answer: A larger surface area provides more area for exchange of nutrients, gases and wastes.

Question 11. A plant cell and an animal cell are placed separately in distilled water. Predict what happens to each and explain the difference.

Answer: Both take up water by osmosis. The animal cell may swell and burst, while the plant cell becomes turgid because its cell wall resists excessive expansion.

Question 12. A cell’s lysosomes suddenly stop functioning. Which cellular problem would most directly appear?

Answer: Waste materials and worn-out cell components would not be broken down efficiently.

Question 13. A scientist observes an organelle with its own DNA and ribosomes. Which organelle(s) could it be? What does this suggest about its evolutionary origin?

Answer: Mitochondria or chloroplasts; their own DNA and ribosomes support the endosymbiotic theory.

Question 14. A student observes onion peel cells and concludes, “These cells cannot be living because I cannot see them moving.” Identify the flaw in the reasoning.

Answer: Cellular movement is not a necessary criterion for life. Onion cells are living plant cells even though they do not move as whole cells.

Question 15. If ribosomes suddenly disappeared from a cell, which cellular process would be affected first and most directly? Why?

Answer: Protein synthesis, because ribosomes are the sites of protein synthesis.

Question 16. Two cells have identical genetic material, but one has developed into a muscle cell and the other into a nerve cell. How is this possible?

Answer: Different genes are expressed in different cells, causing them to produce different proteins and perform specialised functions.

Question 17. A cell contains a well-developed endoplasmic reticulum and Golgi apparatus. What can you predict about its cellular activity?

Answer: It is likely actively synthesising, modifying, packaging and transporting proteins or other cellular products.

Question 18. Why would destroying the mitochondria of a highly active muscle cell affect it more severely than a relatively inactive cell?

Answer: Muscle cells require large amounts of energy for contraction, so they depend heavily on mitochondria for ATP production.

Question 19. A student observes a cell with a cell wall and chloroplasts but no clearly visible nucleus. The student immediately concludes that it is a prokaryotic cell. Is this conclusion valid? Why?

Answer: No. The nucleus may simply not be clearly visible due to the microscope, staining or preparation. Cell wall and chloroplasts alone cannot establish that a cell is prokaryotic.

Question 20. A cell is compared to a city. If the plasma membrane develops a defect and begins allowing every substance to enter freely, what major problem would the cell face?

Answer: The cell would lose control over its internal environment, causing an imbalance in water, ions and other substances and potentially leading to cell damage or death.

1. What process is primarily responsible for the changes observed in ( \displaystyle \text{Solution B} ) and ( \displaystyle \text{Solution C} )?

Answer: Osmosis.

2. Which solution is most likely hypertonic to the cell?

Answer: ( \displaystyle \text{Solution C} ).

3. Why does the plasma membrane pull away from the cell wall in ( \displaystyle \text{Solution C} )?

Answer: Water leaves the cell, causing the cytoplasm and plasma membrane to shrink away from the cell wall (plasmolysis).

4. If the cell from ( \displaystyle \text{Solution C} ) is transferred to distilled water, what would you predict? Give a reason.

Answer: Water will enter the cell by osmosis, causing deplasmolysis and restoration of turgidity.

1. Which cell is likely to have the highest energy requirement?

Answer: ( \displaystyle \text{Cell P} ).

2. Which cell is likely to be actively involved in protein synthesis?

Answer: ( \displaystyle \text{Cell Q} ).

3. Which cell is best adapted for photosynthesis?

Answer: ( \displaystyle \text{Cell R} ).

4. What does this case demonstrate about cell organelles and cell specialisation?

Answer: Different cells contain different numbers/types of organelles according to their specialised functions.

1. Why does the cell not die immediately after removal of the nucleus?

Answer: Existing proteins and cellular machinery can continue functioning temporarily.

2. What important function of the nucleus is demonstrated by the later decline in cellular activity?

Answer: The nucleus controls cellular activities through genetic information.

3. Which molecule present in the nucleus carries hereditary information?

Answer: DNA.

4. Would the same effect be expected if only a lysosome were removed? Explain.

Answer: No. Removal of a single lysosome would mainly affect intracellular digestion/waste breakdown rather than overall genetic control.

1. Which cell structure acts as the selective security boundary?

Answer: Plasma membrane.

2. Which organelle would be compared with the power station?

Answer: Mitochondria.

3. If the packaging department stops functioning, which organelle is most likely affected?

Answer: Golgi apparatus.

4. Why is it incorrect to say that each organelle works completely independently?

Answer: Organelles work together; for example, proteins synthesised by ribosomes may be modified and packaged by the Golgi apparatus.

1. What type of cells could A and B most likely represent?

Answer: ( \displaystyle \text{Cell A} \rightarrow \text{animal cell} ); ( \displaystyle \text{Cell B} \rightarrow \text{plant cell} ).

2. Why do both cells initially swell?

Answer: Water enters because the surrounding distilled water is hypotonic to the cell contents.

3. What structural feature protects ( \displaystyle \text{Cell B} ) from bursting?

Answer: Cell wall.

4. Name the movement of water responsible for this observation.

Answer: Osmosis.

1. Which cell would show the most direct reduction in protein synthesis?

Answer: ( \displaystyle \text{Cell P} ).

2. Which cell would face the greatest difficulty in meeting its energy requirements?

Answer: ( \displaystyle \text{Cell Q} ).

3. Which cell would have difficulty digesting worn-out cellular components?

Answer: ( \displaystyle \text{Cell R} ).

4. Which cell would have difficulty modifying, packaging and transporting certain cellular products?

Answer: ( \displaystyle \text{Cell S} ).

5. If the chemical affected all four structures simultaneously, why might the cell eventually die?

Answer: Multiple essential cellular functions would fail, disrupting metabolism, protein production, waste removal and transport.

1. Is the student’s conclusion scientifically valid?

Answer: No. A nucleus may be present but not visible because of staining, focusing or the orientation of the cell.

2. Which observation strongly suggests that this is a plant cell?

Answer: Presence of a cell wall and chloroplasts.

3. Give two possible reasons why the nucleus may not be visible.

Answer: Poor staining, incorrect focusing, cell orientation, or insufficient microscope resolution.

4. Which statement provides stronger evidence about the cell type: absence of a visible nucleus or presence of chloroplasts? Explain.

Answer: Presence of chloroplasts provides stronger evidence for a plant/eukaryotic cell; absence of a visible nucleus does not prove absence of a nucleus.