# Describe how nitrogen in the proteins of a living plant becomes available to other plants as nitrate ions in the soil.

> Cambridge International IGCSE Biology (0610) — 19.3 Nutrient cycles · Describe · 4 marks

## Mark scheme (4 marks)

1. Decomposers (bacteria/fungi) break down proteins in dead plant material, producing ammonium ions
2. Nitrifying bacteria convert ammonium ions to nitrite ions, and then to nitrate ions
3. Nitrate ions are absorbed by plant roots from the soil
4. Plants use nitrate ions to make amino acids / proteins

## Key terms

- [nitrate ions](https://www.gradenine.co.uk/glossary/nitrate-ions)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-nitrogen-in-the-proteins-9400c1b9) · Published by Druglandscape Ltd.