# Explain how the structure of starch makes it suited to its function as an energy storage molecule in plant cells.

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

## Mark scheme (4 marks)

1. Starch is a polysaccharide composed of many glucose monomers joined by glycosidic bonds, providing a large store of chemical energy.
2. Starch is insoluble in water, so it does not affect the water potential / osmotic balance of the cell.
3. Starch is compact / coiled (amylose forms a helix; amylopectin is branched), allowing large quantities to be stored in a small volume.
4. Starch can be rapidly hydrolysed by enzymes (e.g. amylase) to release glucose monomers when energy is needed, making it a readily mobilisable energy store.

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard 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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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-starch-601d6137) · Published by Druglandscape Ltd.