# Explain how the water potential of a plant cell changes as the cell absorbs water by osmosis and approaches full turgor.

> IB DP Biology Standard Level (2023 syllabus) — D2.3 Water potential · Explain · 4 marks

## Mark scheme (4 marks)

1. As water enters the cell by osmosis, the solute concentration of the cytoplasm/vacuole decreases, so the solute potential (ψs) becomes less negative.
2. The inflow of water increases the volume of the vacuole/cell, generating an increasing pressure (turgor pressure / pressure potential, ψp) against the cell wall.
3. Water potential (ψ) is the sum of solute potential and pressure potential (ψ = ψs + ψp); as both ψs becomes less negative and ψp increases, the overall water potential of the cell rises.
4. At full turgor the water potential of the cell equals the water potential of the surrounding solution, so net osmosis stops / water potential gradient is zero.

## Key terms

- [water potential](https://www.gradenine.co.uk/glossary/water-potential)
- [osmosis](https://www.gradenine.co.uk/glossary/osmosis)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](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-how-the-water-potential-of-70a92e06) · Published by Druglandscape Ltd.