# A piece of celery is left out of water for several hours and becomes limp. It is then placed in distilled water for one hour. Explain why the celery becomes firm again after being placed in distilled water.

> Cambridge International IGCSE Biology (0610) — 3.2 Osmosis · Explain · 4 marks

## Mark scheme (4 marks)

1. Distilled water has a higher water concentration / water potential than the celery cells
2. Water enters the celery cells by osmosis (through the partially permeable membrane)
3. The cells take in water and swell / increase in volume
4. The cells become turgid / turgor pressure increases, pushing the cell membrane against the cell wall, making the celery firm

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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