A student observing a cell under a light microscope notices several distinct organelles. Describe the function of the nucleus, mitochondria, and chloroplasts in a plant cell, and explain why animal cells lack one of these organelles.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student is examining a palisade mesophyll cell from a leaf and an animal cell. They observe that the two cell types share some organelles but differ in others.
Model answer (4 marks)
The nucleus contains the cell’s genetic material and controls the activities of the cell.
The mitochondria are the site of aerobic respiration, releasing energy (as ATP) from glucose.
The chloroplasts are the site of photosynthesis; they contain chlorophyll which absorbs light energy.
Animal cells lack chloroplasts because they do not photosynthesise – they obtain energy from food rather than light.
The mitochondria are the site of aerobic respiration, releasing energy (as ATP) from glucose.
The chloroplasts are the site of photosynthesis; they contain chlorophyll which absorbs light energy.
Animal cells lack chloroplasts because they do not photosynthesise – they obtain energy from food rather than light.
Examiner tips
- Use the exact wording from the mark scheme – e.g. ‘site of aerobic respiration’ and ‘site of photosynthesis’. Explain the absence of chloroplasts in a single sentence. Keep each point brief and to the point to fit the 4‑mark limit.
Common mistakes
- Mixing up the functions of mitochondria and chloroplasts. Forgetting to mention that animal cells lack chloroplasts. Using vague terms like ‘energy’ without specifying ATP or photosynthesis.
Mark scheme (4 marks)
- The nucleus contains the cell's genetic material and controls the activities of the cell.
- Mitochondria are the site of aerobic respiration, releasing energy (as ATP) from glucose.
- Chloroplasts are the site of photosynthesis; they contain chlorophyll which absorbs light energy.
- Animal cells lack chloroplasts because they do not photosynthesise / they obtain energy from food rather than light.
Key terms in this question
nucleus · mitochondria · chloroplasts
Related
- Revision notes: Cell structures →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
More Cell structures questions
- Explain why plant cells have both a cell membrane and a cell wall, whilst animal…
- A palisade mesophyll cell and a human cheek cell are both eukaryotic cells. Expl…
- A bacterial cell is a prokaryotic cell. Explain why bacterial cells do not have …
- A yeast cell is a eukaryotic cell. Explain why a yeast cell contains mitochondri…