# Explain why the cell membrane is important for controlling what enters and leaves a cell.

> Edexcel GCSE Biology (1BI0) — 1.1 Cell biology · Explain · 4 marks

> All living cells are surrounded by a cell membrane. The cell membrane is described as selectively permeable.

## Mark scheme (4 marks)

1. The cell membrane is selectively permeable, meaning it allows some substances to pass through but not others
2. This allows useful substances such as glucose and oxygen to enter the cell
3. Waste products such as carbon dioxide or urea can leave the cell
4. This maintains a stable internal environment / prevents harmful substances from entering the cell, keeping the cell functioning correctly

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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/explain-why-the-cell-membrane-is-1e254bcf) · Published by Druglandscape Ltd.