# Explain how the structure of cellulose differs from the structure of starch, and explain how these structural differences relate to the different functions of each molecule in plant cells.

> AQA A-Level Biology (7402) — 3.1.2 Carbohydrates · Explain · 5 marks

## Mark scheme (5 marks)

1. Cellulose has straight/unbranched chains whereas starch has branched chains (or helical/coiled chains)
2. Cellulose chains lie parallel and form cross-links / hydrogen bonds between chains, creating microfibrils
3. This gives cellulose high tensile strength / rigidity, so it supports and strengthens the cell wall
4. Starch is insoluble, so it does not affect the water potential of the cell / does not cause osmosis
5. Starch can be hydrolysed / broken down to release glucose for respiration / energy when needed

## Key terms

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

## Related

- [Revision notes for AQA A-Level Biology (7402)](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-structure-of-cellulose-abc691e7) · Published by Druglandscape Ltd.