# The cell membrane is described as selectively permeable. Explain how the cell membrane controls the movement of substances into and out of the cell, and why this selective permeability is important for the cell.

> Eduqas A-Level Biology — 1.3 Cell membranes and transport · Explain · 5 marks

## Mark scheme (5 marks)

1. The cell membrane acts as a selectively permeable barrier
2. The cell membrane controls the movement of substances into the cell
3. The cell membrane controls the movement of substances out of the cell
4. The cell membrane has receptor molecules on its surface for cell-to-cell signalling
5. Selective permeability is important because it maintains the correct internal conditions / prevents harmful substances from entering or essential substances from being lost

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/the-cell-membrane-is-described-as-a06c5159) · Published by Druglandscape Ltd.