These eight questions follow the chapter in order, from comparison to calculation. Write each answer before opening the explanation.
The lessons are in cells and organisation. Log any slips in the mistake log and paper-error review.
Questions
1. State two structures found in a palisade cell but not in a cheek cell. (2 marks)
Answer
Cell wall and chloroplasts. A large permanent vacuole is also accepted. Name the structure only for the cell that has it, and keep the cheek cell as the comparison.
2. Explain why a plant cell keeps a fixed shape but an animal cell does not. (2 marks)
Answer
The plant cell has a rigid cell wall made of cellulose, so it resists the pressure of water inside. The animal cell has only a flexible cell membrane, so its shape can change.
3. A cell has a very large number of ribosomes. State what this tells you about the cell’s activity. (2 marks)
Answer
Ribosomes make proteins, so the cell makes large amounts of protein, for example enzymes for secretion. Saying “it has many ribosomes” is not enough. The link to protein making gives the mark.
4. The Golgi apparatus is sometimes called the packaging centre. Describe what it does to a protein after the protein arrives. (2 marks)
Answer
It modifies the protein and packages it into vesicles. The vesicles carry the protein to the cell membrane, where it is released.
5. A sperm cell has a long tail and many mitochondria. Explain how each feature helps the cell. (3 marks)
Answer
The long tail moves the sperm forward, so it can swim towards the ovum. The mitochondria release energy by respiration, so the tail can keep beating. The feature-effect link is needed in both parts.
6. A root hair cell has a long extension and no chloroplasts. Explain why each is suitable. (3 marks)
Answer
The extension gives a large surface area, so more water and mineral ions can be absorbed. The cell is underground, so there is no light and chloroplasts would serve no purpose.
7. An onion cell is 50 µm long. A drawing of it is 40 mm long.
Calculate the magnification. (2 marks)
Answer
Convert: 40 mm = 40 000 µm. Magnification = 40 000 ÷ 50 = ×800.
8. A micrograph at ×250 shows a cell 18 mm long. A student says the actual length is 72 µm.
Is this correct? Show your working. (3 marks)
Answer
Convert: 18 mm = 18 000 µm. Actual size = 18 000 ÷ 250 = 72 µm. The student is correct.
Check: 72 × 250 = 18 000, which matches the image length.
If you got these wrong
- Questions 1 and 2: revisit comparing animal and plant cells.
- Questions 3 to 5: open relating organelles to functions.
- Question 6: open explaining specialised cells and organisation.
- Questions 7 and 8: open calculating image magnification with consistent units.
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