# Osmosis is an important process that occurs across cell membranes. Explain what happens to a plant cell when it is placed in a solution that has a lower water concentration than the cell's contents.

> WJEC A-Level Biology (Wales) — 1.3 Cell membranes and transport · Explain · 5 marks

> A student placed a piece of plant tissue into a concentrated salt solution and left it for 30 minutes. When the tissue was removed, it felt limp and flexible rather than firm.

## Mark scheme (5 marks)

1. Water moves out of the cell by osmosis
2. Water moves from a higher water concentration (inside the cell) to a lower water concentration (in the solution) across the selectively permeable cell membrane
3. The vacuole and cytoplasm lose water, causing the cell to shrink
4. The cell membrane pulls away from the cell wall (plasmolysis occurs)
5. The cell becomes flaccid / loses turgor pressure, so the tissue feels limp

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](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/osmosis-is-an-important-process-that-65f2458a) · Published by Druglandscape Ltd.