# A group of students investigated anaerobic respiration in yeast. They placed yeast and glucose solution in a sealed flask at 30 °C and collected the gas produced over 20 minutes. Explain what happens inside the yeast cells during anaerobic respiration and why the gas collected causes limewater to turn cloudy.

> Pearson Edexcel A-Level Biology A (9BI0) — 4.1 Cellular respiration · Explain · 5 marks

> Yeast can respire both aerobically and anaerobically. When oxygen is unavailable, yeast carries out anaerobic respiration, producing different products compared to aerobic respiration.

## Mark scheme (5 marks)

1. Anaerobic respiration occurs without oxygen
2. Glucose is broken down / glucose is the substrate for anaerobic respiration
3. Ethanol (alcohol) and carbon dioxide are produced as products
4. The gas collected is carbon dioxide
5. Carbon dioxide turns limewater cloudy / reacts with limewater to form a white precipitate (calcium carbonate)

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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-group-of-students-investigated-anaerobic-7ac76480) · Published by Druglandscape Ltd.