# A scientist investigates the effect of temperature on the permeability of cell membranes. Pieces of beetroot are placed into water at different temperatures. At higher temperatures, more red pigment leaks out of the beetroot cells into the surrounding water. Explain why increasing temperature causes more pigment to leak out of the beetroot cells.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 1.6 Membranes and transport · Explain · 5 marks

> Beetroot cells contain a red pigment stored in the vacuole. The pigment is normally retained inside the cell by the cell membrane. When the membrane is damaged, the pigment can pass through into the surrounding water.

## Mark scheme (5 marks)

1. The cell membrane is made of a phospholipid bilayer (which controls what enters and leaves the cell)
2. Increasing temperature provides more energy / causes phospholipid molecules to move more
3. The membrane becomes more fluid / less stable / more permeable
4. At very high temperatures, proteins in the membrane are denatured
5. The pigment molecules can therefore pass through / diffuse out of the damaged membrane into the surrounding water

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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/a-scientist-investigates-the-effect-of-3aff4539) · Published by Druglandscape Ltd.