# Explain how the structures of starch and glycogen make them suitable for energy storage in plant and animal cells respectively.

> IB DP Biology Higher Level (2023 syllabus) — B1.1 Carbohydrates and lipids · Explain · 4 marks

## Mark scheme (4 marks)

1. Both starch and glycogen are polymers of alpha-glucose, linked by glycosidic bonds, making them chemically inert / stable for storage
2. Both molecules are compact / coiled (helical in starch; highly branched in glycogen), allowing large amounts of glucose to be stored in a small volume / without osmotic effects
3. Glycogen is more highly branched than starch, providing more non-reducing ends for rapid enzymatic hydrolysis / quick release of glucose when energy demand is high
4. Glucose is released by hydrolysis of glycosidic bonds for use in respiration, so storage as a polymer allows controlled / regulated release of glucose on demand

## 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)
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