# Describe how nitrogen-fixing bacteria and nitrifying bacteria contribute to making nitrogen available for plant growth.

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

## Mark scheme (4 marks)

1. Nitrogen-fixing bacteria convert atmospheric nitrogen gas into ammonia (nitrogen-containing compounds)
2. Nitrifying bacteria convert ammonium ions into nitrite and then nitrate ions (in the soil)
3. Plants absorb nitrate ions from the soil (through their roots)
4. Plants use the nitrogen-containing compounds (nitrates) to make proteins/amino acids for growth

## Key terms

- [nitrogen-fixing bacteria](https://www.gradenine.co.uk/glossary/nitrogen-fixing-bacteria)
- [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 "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-nitrogen-fixing-bacteria-and-nitrifying-2ca3a951) · Published by Druglandscape Ltd.