# Explain the role of decomposers in the carbon cycle.

> AQA A-Level Biology (7402) — 3.5.4 Nutrient Cycles · Explain · 5 marks

> Dead organisms and waste materials contain carbon compounds. These materials must be broken down before carbon can be returned to the atmosphere.

## Mark scheme (5 marks)

1. Decomposers (bacteria and fungi) break down / digest dead organisms and waste material
2. Decomposers release enzymes to break down organic compounds (extracellular digestion)
3. Carbon compounds in dead material are broken down into simpler substances / carbon is released as carbon dioxide
4. This release of carbon dioxide occurs through respiration by the decomposers
5. This returns carbon (as carbon dioxide) to the atmosphere, making it available for photosynthesis

## Key terms

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

## Related

- [Revision notes for AQA A-Level Biology (7402)](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-in-6125296f) · Published by Druglandscape Ltd.