Explain how yeast is used in the production of bread.

WJEC GCSE Biology (Wales) — 2.7 Micro-organisms and their applications · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Yeast cells carry out anaerobic respiration (fermentation) when oxygen is scarce in dough. They metabolise sugars, mainly glucose, to produce energy. During this process carbon dioxide is released as a waste product. The CO₂ gas forms bubbles in the dough, causing it to rise and giving bread its light, airy texture.

Examiner tips

Use the term ‘fermentation’ and ‘anaerobic respiration’ to show understanding of the process.
Mention that glucose is the sugar broken down.
Explain that CO₂ is the gas that makes the dough rise.
Show the link between rising dough and the final bread texture.

Common mistakes

Confusing aerobic respiration with fermentation.
Failing to identify CO₂ as the key gas produced.
Not linking the rise of dough to the final bread texture.

Mark scheme (4 marks)

Yeast carries out anaerobic respiration / fermentation
Yeast breaks down / respires sugars / glucose
Carbon dioxide is produced / released
Carbon dioxide causes the dough to rise / makes the bread light

Key terms in this question

yeast