# Yeast cells are used in bread making. Explain how yeast cells produce carbon dioxide when making bread dough rise.

> Eduqas GCSE Biology — 1.2.1 Aerobic and anaerobic respiration · Explain · 4 marks

> Bread dough is made by mixing flour, water, sugar and yeast. The dough is left in a warm place before baking. During this time the dough increases in volume.

## Mark scheme (4 marks)

1. Yeast carries out anaerobic respiration (in the absence of oxygen / when oxygen is limited)
2. Glucose is broken down / used as a reactant
3. Carbon dioxide (and ethanol/alcohol) are produced as products
4. The carbon dioxide gas becomes trapped in the dough, causing it to expand / rise

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/yeast-cells-are-used-in-bread-9efdd3e8) · Published by Druglandscape Ltd.