# Explain how the addition of solutes to a plant cell affects its water potential and the direction of osmosis between that cell and an adjacent cell with a higher water potential.

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

> A mesophyll cell in a leaf accumulates dissolved sugars following active loading of sucrose from the phloem. The cell is surrounded by neighbouring mesophyll cells that have not accumulated solutes to the same extent.

## Mark scheme (4 marks)

1. Adding solutes lowers (makes more negative) the solute potential (Ψs) of the cell
2. This lowers the overall water potential (Ψ) of the sugar-loaded cell, making it more negative than the adjacent cell
3. Water moves by osmosis from the region of higher water potential (adjacent cell) to the region of lower water potential (sugar-loaded cell)
4. As water enters, turgor pressure / pressure potential (Ψp) increases, which raises the water potential of the sugar-loaded cell until equilibrium is reached

## Key terms

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

## 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-how-the-addition-of-solutes-684758fc) · Published by Druglandscape Ltd.