# Explain why two different proteases, pepsin and trypsin, are needed for the complete chemical digestion of proteins in the alimentary canal.

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

## Mark scheme (4 marks)

1. Pepsin works in the stomach where conditions are acidic / low pH (approximately pH 1.5), which is its optimum pH.
2. Trypsin works in the small intestine where conditions are neutral or slightly alkaline, which is its optimum pH.
3. Each enzyme would be denatured / stop working in the wrong pH / in the other enzyme's location.
4. Having both enzymes ensures protein is broken down / digested to amino acids throughout the alimentary canal / completely.

## Key terms

- [protease](https://www.gradenine.co.uk/glossary/protease)
- [pepsin](https://www.gradenine.co.uk/glossary/pepsin)
- [trypsin](https://www.gradenine.co.uk/glossary/trypsin)
- [alimentary canal](https://www.gradenine.co.uk/glossary/alimentary-canal)

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](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/explain-why-two-different-proteases-pepsin-2d0bf451) · Published by Druglandscape Ltd.