# Explain the role of decomposers and nitrifying bacteria in making nitrogen available for plant uptake.

> Edexcel GCSE Biology (1BI0) — 9.3 Material cycles · Explain · 4 marks

> Nitrogen is an essential element for plant growth. Plants cannot use atmospheric nitrogen gas directly, so they depend on a series of processes in the nitrogen cycle to obtain nitrogen in a usable form.

## Mark scheme (4 marks)

1. Decomposers break down dead plant and animal material / proteins / urea into ammonia (ammonium ions)
2. Nitrifying bacteria convert ammonium ions into nitrite and then into nitrate ions
3. Nitrate ions are absorbed by plants (through roots) / used by plants to make proteins
4. Both processes are linked / decomposers produce the ammonia that nitrifying bacteria then act upon, so together they return nitrogen to a form usable by plants

## Key terms

- [decomposers](https://www.gradenine.co.uk/glossary/decomposers)
- [nitrifying bacteria](https://www.gradenine.co.uk/glossary/nitrifying-bacteria)

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-the-role-of-decomposers-and-09ba18ec) · Published by Druglandscape Ltd.