# Proteases and lipases are both enzymes involved in digestion. Explain why a protease enzyme cannot break down a lipid molecule, and describe what happens when a protease is used to digest a protein at its optimum temperature.

> WJEC A-Level Biology (Wales) — 1.4 Biological reactions and enzymes · Explain and Describe · 5 marks

## Mark scheme (5 marks)

1. Each enzyme has an active site with a specific/complementary shape
2. The lipid molecule does not have a complementary shape to the protease active site / is not the correct/matching substrate
3. Reference to the lock and key hypothesis to explain enzyme specificity
4. The protein substrate enters the active site of the protease, forming an enzyme-substrate complex
5. The protein is broken down into amino acids / products are released and the enzyme is unchanged and can be reused

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain and Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/proteases-and-lipases-are-both-enzymes-bcb7feeb) · Published by Druglandscape Ltd.