# A brewery uses yeast to produce beer. The yeast is added to a sealed container containing glucose solution. After several hours, the liquid contains ethanol and bubbles of gas are observed. Explain what type of respiration the yeast is carrying out and why, describing the process that is occurring.

> OCR A-Level Biology B — Advancing Biology (H422) — 4.2 Respiration · Explain · 5 marks

> Yeast is a microorganism used in brewing. When sealed containers of glucose solution are inoculated with yeast, the yeast produces ethanol and a gas over several hours.

## Mark scheme (5 marks)

1. The yeast is carrying out anaerobic respiration
2. Because the container is sealed / there is no (sufficient) oxygen available
3. Glucose is broken down / used as a reactant in the process
4. Ethanol (and carbon dioxide) are produced as products
5. Energy is released from glucose during this process

## Key terms

- [glucose](https://www.gradenine.co.uk/glossary/glucose)
- [ethanol](https://www.gradenine.co.uk/glossary/ethanol)

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](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-brewery-uses-yeast-to-produce-acb4840a) · Published by Druglandscape Ltd.