# Explain how decomposers and nitrifying bacteria work together to make nitrogen available for plant uptake.

> Edexcel GCSE Biology (1BI0) — 9.1 Ecosystems · Explain · 4 marks

> Plants require nitrogen-containing compounds to synthesise proteins. Although nitrogen gas makes up approximately 78% of the atmosphere, plants cannot use it directly.

## Mark scheme (4 marks)

1. Decomposers break down dead plant/animal material (proteins and urea) into ammonia / ammonium ions
2. Nitrifying bacteria convert ammonium ions into nitrite ions and then nitrate ions (in the soil)
3. Nitrate ions are absorbed by plant roots (from the soil)
4. Plants use nitrate ions to synthesise proteins / nitrogen-containing compounds

## 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-how-decomposers-and-nitrifying-bacteria-1f7cb0e3) · Published by Druglandscape Ltd.