# Explain why yeast cells switch to anaerobic respiration when oxygen is no longer available, and describe the products that are released during this process.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.7 Respiration · Explain · 4 marks

> Yeast is a single-celled fungus used in bread-making and brewing. When yeast is provided with a plentiful supply of glucose, it respires. However, the availability of oxygen can change depending on the conditions in which the yeast is kept.

## Mark scheme (4 marks)

1. Yeast switches to anaerobic respiration because oxygen is unavailable / absent (so aerobic respiration cannot occur)
2. Anaerobic respiration still releases energy (from glucose) for the yeast cell
3. Ethanol (alcohol) is produced during anaerobic respiration in yeast
4. Carbon dioxide is also produced during anaerobic respiration in yeast

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-yeast-cells-switch-to-93e21b6a) · Published by Druglandscape Ltd.