# Explain how signal amplification occurs during the response of a target cell to adrenaline, including the roles of adenylyl cyclase, cyclic AMP, and protein kinase A.

> IB DP Biology Higher Level (2023 syllabus) — C2.1 Chemical signalling (HL only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Adrenaline binds its receptor, activating a G-protein, which in turn activates adenylyl cyclase
2. Each activated adenylyl cyclase converts many ATP molecules into cyclic AMP (cAMP), so one hormone–receptor event produces many second messenger molecules
3. cAMP activates protein kinase A (PKA), and each active PKA molecule can phosphorylate many substrate proteins / enzymes
4. Amplification arises because each step in the cascade multiplies the number of active molecules, so a very small number of hormone–receptor binding events produces a very large cellular response

## Key terms

- [signal amplification](https://www.gradenine.co.uk/glossary/signal-amplification)
- [adenylyl cyclase](https://www.gradenine.co.uk/glossary/adenylyl-cyclase)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](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/explain-how-signal-amplification-occurs-during-6def133d) · Published by Druglandscape Ltd.