# Explain what happens to a plant cell when it is placed in pure water, including the role of the cell wall.

> AQA A-Level Biology (7402) — 3.2.3 Transport Across Membranes · Explain · 5 marks

> A student places a flaccid plant cell into a beaker of pure water and observes changes over time.

## Mark scheme (5 marks)

1. Pure water has a higher water concentration than the cell contents / cell sap
2. Water moves into the cell by osmosis (through the partially permeable membrane)
3. The vacuole / cell contents swell and the cell becomes turgid
4. The cell contents push against the cell wall, generating pressure / the cell wall is pushed outward
5. The cell wall is inelastic / rigid, so it resists further expansion and prevents the cell from bursting

## Key terms

- [cell wall](https://www.gradenine.co.uk/glossary/cell-wall)

## 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-what-happens-to-a-plant-e5f6e526) · Published by Druglandscape Ltd.