# Explain why the rate of photosynthesis in a plant increases as light intensity increases, but only up to a certain point.

> AQA A-Level Biology (7402) — 3.5.1 Photosynthesis · Explain · 5 marks

## Mark scheme (5 marks)

1. Light is a reactant / energy source needed for photosynthesis
2. More light means more energy available so the rate of photosynthesis increases
3. Rate levels off / stops increasing beyond a certain light intensity
4. Another factor becomes limiting / rate is limited by another factor such as carbon dioxide concentration or temperature
5. A limiting factor is something that limits the rate of photosynthesis when it is in short supply

## Key terms

- [rate of photosynthesis](https://www.gradenine.co.uk/glossary/rate-of-photosynthesis)
- [light intensity](https://www.gradenine.co.uk/glossary/light-intensity)

## Related

- [Revision notes for AQA A-Level Biology (7402)](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-why-the-rate-of-photosynthesis-04c7903a) · Published by Druglandscape Ltd.