# Describe the role of hydrochloric acid in the stomach and explain why the enzyme lipase is secreted into the duodenum rather than acting in the stomach.

> Cambridge International IGCSE Biology (0610) — 7.4 Chemical digestion · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. Hydrochloric acid kills harmful microorganisms / bacteria in food
2. Hydrochloric acid provides an optimum (low / acidic) pH for protease / pepsin activity
3. The stomach is too acidic / has too low a pH for lipase to function effectively
4. Bile neutralises stomach acid in the duodenum, providing a neutral / slightly alkaline pH that is the optimum for lipase activity

## Key terms

- [hydrochloric acid](https://www.gradenine.co.uk/glossary/hydrochloric-acid)
- [lipase](https://www.gradenine.co.uk/glossary/lipase)
- [duodenum](https://www.gradenine.co.uk/glossary/duodenum)

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/describe-the-role-of-hydrochloric-acid-9730a064) · Published by Druglandscape Ltd.