A yeast cell is a eukaryotic cell. Explain why a yeast cell contains mitochondria but does not contain chloroplasts.

OCR GCSE Biology A: Gateway Science (J247) — B1.1 Cell structures · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Yeast are single-celled fungi that can be found living on the surface of fruit. They obtain energy by breaking down sugars such as glucose.

Model answer (4 marks)

A yeast cell contains mitochondria because they are the site of aerobic respiration, which releases energy from glucose that the cell needs for life processes.

It does not contain chloroplasts because chloroplasts are the site of photosynthesis and contain chlorophyll to absorb light energy.

Yeast cannot photosynthesise; it is not a photosynthetic organism and therefore does not carry out photosynthesis to make its own food.

Examiner tips

Use the exact terms ‘mitochondria’, ‘aerobic respiration’, ‘chloroplasts’, ‘photosynthesis’, ‘chlorophyll’
Explain the function of each organelle before stating why it is present or absent
Keep the answer concise – 4 marks, so one sentence per point

Common mistakes

Confusing mitochondria with chloroplasts, or vice versa
Failing to mention that yeast uses glucose, not light, for energy
Using vague language such as ‘energy’ without specifying aerobic respiration or photosynthesis

Mark scheme (4 marks)

Mitochondria are the site of aerobic respiration
Yeast needs to release energy (from glucose / organic compounds) to carry out life processes
Chloroplasts are the site of photosynthesis / contain chlorophyll to absorb light energy
Yeast cannot photosynthesise because it is not a photosynthetic organism / does not carry out photosynthesis to make its own food

Key terms in this question

mitochondria · chloroplasts · eukaryotic cell