# A student runs a 400 m race. During the race, her muscles begin to respire anaerobically. Describe what happens during anaerobic respiration in human muscle cells and explain why this type of respiration cannot continue indefinitely.

> AQA A-Level Biology (7402) — 3.5.2 Respiration · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Anaerobic respiration occurs without oxygen
2. Glucose is broken down / converted
3. Lactic acid is produced as the product
4. Less energy / ATP is released compared to aerobic respiration
5. Lactic acid builds up in the muscles / blood and causes fatigue / muscle pain / cramp, so the muscles cannot continue to work efficiently

## Key terms

- [anaerobic respiration](https://www.gradenine.co.uk/glossary/anaerobic-respiration)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/a-student-runs-a-400-m-f6b80d55) · Published by Druglandscape Ltd.