# A student sprints 400 metres and then rests. During the sprint, the student's muscles respire anaerobically as well as aerobically. Explain why anaerobic respiration occurs during the sprint and describe what happens in the student's body during the recovery period after the sprint.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.1 Cellular respiration · Explain · 5 marks

> During intense exercise, the body cannot always supply muscles with oxygen fast enough to meet energy demands.

## Mark scheme (5 marks)

1. During sprinting, oxygen cannot be delivered to the muscles fast enough / muscles do not receive sufficient oxygen to meet the energy demand
2. Anaerobic respiration produces energy (ATP) without oxygen / allows energy release to continue when oxygen is limited
3. Anaerobic respiration in muscles produces lactic acid
4. During recovery, the student breathes faster/deeper to take in extra oxygen / oxygen debt must be repaid
5. The extra oxygen is used to oxidise / break down lactic acid (into carbon dioxide and water)

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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/a-student-sprints-400-metres-and-f9816a23) · Published by Druglandscape Ltd.