# A student regularly trains by cycling long distances. During a training session, the student's muscles use glucose for respiration. Explain how blood glucose concentration is maintained during a long training session when glucose is being used rapidly by muscles.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 7 Run for your Life · Explain · 5 marks

> During prolonged exercise, muscles respire continuously, consuming large amounts of glucose. The body must respond to prevent blood glucose levels from falling dangerously low.

## Mark scheme (5 marks)

1. Blood glucose concentration falls / decreases during exercise
2. The pancreas detects the low blood glucose concentration and secretes glucagon
3. Glucagon causes glycogen to be broken down to glucose in the liver
4. Glucose is released into the bloodstream, raising blood glucose concentration back to normal
5. This is an example of homeostasis / negative feedback, maintaining a stable internal environment

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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-student-regularly-trains-by-cycling-4d3b702b) · Published by Druglandscape Ltd.