Explain how nitrogen found in the protein of a dead plant becomes available to a living plant growing in the same soil.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Decomposers such as bacteria and fungi break down the dead plant’s protein.
The nitrogen in the protein is converted into simpler compounds, mainly ammonium (NH4+) and then into nitrates (NO3−) in the soil.
The living plant takes up these nitrogen compounds through its roots.
The plant incorporates the nitrogen into new proteins, building cells and enabling growth.
The nitrogen in the protein is converted into simpler compounds, mainly ammonium (NH4+) and then into nitrates (NO3−) in the soil.
The living plant takes up these nitrogen compounds through its roots.
The plant incorporates the nitrogen into new proteins, building cells and enabling growth.
Examiner tips
- Use the word ‘decomposers’ and name bacteria/fungi. Show the conversion to ammonium and nitrates. Mention root uptake. Explain use in new protein and growth.
Common mistakes
- Omitting the step of decomposition. Failing to name the nitrogen compounds (ammonium/nitrate). Not linking nitrogen uptake to protein synthesis or plant growth.
Mark scheme (4 marks)
- Decomposers (bacteria/fungi) break down the dead plant material / protein
- Nitrogen-containing compounds / proteins are broken down into simpler nitrogen compounds / ammonium / nitrates in the soil
- The living plant absorbs the nitrogen compounds / nitrates / minerals through its roots
- The plant uses these nitrogen compounds to make new protein / build new cells / grow
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
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