# A student investigates gas exchange in a plant. They place a leafy shoot in bright light and then move it into complete darkness. Describe how the movement of carbon dioxide and oxygen through the stomata changes when the plant is moved from bright light into complete darkness.

> AQA A-Level Biology (7402) — 3.3.2 Gas Exchange · Describe · 5 marks

## Mark scheme (5 marks)

1. In bright light, the plant carries out photosynthesis
2. In bright light, carbon dioxide moves into the leaf (through stomata) for photosynthesis
3. In bright light, oxygen moves out of the leaf (through stomata) as a product of photosynthesis
4. In darkness, photosynthesis stops so the plant only respires
5. In darkness, carbon dioxide moves out of the leaf and oxygen moves into the leaf (through stomata) for respiration

## Key terms

- [stomata](https://www.gradenine.co.uk/glossary/stomata)
- [gas exchange](https://www.gradenine.co.uk/glossary/gas-exchange)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-investigates-gas-exchange-in-467556bc) · Published by Druglandscape Ltd.