# Explain the relationship between turgor pressure, solute potential, and water potential in a fully turgid plant cell.

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

## Mark scheme (4 marks)

1. Water potential (Ψ) equals solute potential (Ψs) plus pressure potential (Ψp) / Ψ = Ψs + Ψp
2. In a fully turgid cell, turgor pressure (pressure potential) is at its maximum positive value, pushing outward against the cell wall
3. Solute potential remains negative (due to dissolved solutes lowering the free energy of water), and in a fully turgid cell solute potential becomes less negative than in a flaccid cell because the cell volume has increased / solutes are diluted
4. In a fully turgid cell, water potential equals zero (or is equal to the water potential of pure water / surroundings) because the positive pressure potential exactly offsets the negative solute potential, so there is no net movement of water

## Key terms

- [water potential](https://www.gradenine.co.uk/glossary/water-potential)
- [solute potential](https://www.gradenine.co.uk/glossary/solute-potential)
- [turgor pressure](https://www.gradenine.co.uk/glossary/turgor-pressure)
- [fully turgid](https://www.gradenine.co.uk/glossary/fully-turgid)

## Related

- [Revision notes for IB DP Biology Higher 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-the-relationship-between-turgor-pressure-7340d85e) · Published by Druglandscape Ltd.