# Explain why the nitrogen cycle is important for plants, and describe how nitrogen from the atmosphere is made available to plants in the soil.

> WJEC GCSE Biology (Wales) — 1.6.2 Nutrient cycles · Explain and Describe · 4 marks

## Mark scheme (4 marks)

1. Plants need nitrogen to make proteins (or nucleic acids / DNA)
2. Nitrogen gas in the atmosphere cannot be used directly by plants
3. Nitrogen-fixing bacteria (in soil or root nodules) convert nitrogen gas into ammonia / nitrates / nitrogen compounds
4. Plants absorb nitrates (or nitrogen compounds / ammonium ions) from the soil through their roots

## Key terms

- [nitrogen cycle](https://www.gradenine.co.uk/glossary/nitrogen-cycle)

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain and Describe" 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-why-the-nitrogen-cycle-is-f95fdca2) · Published by Druglandscape Ltd.