# Explain how the structure of chitin makes it suitable for its role as a structural polysaccharide in the exoskeletons of arthropods and the cell walls of fungi.

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

## Mark scheme (4 marks)

1. Chitin is a polysaccharide composed of repeating N-acetylglucosamine (NAG) monomers linked by β-1,4-glycosidic bonds.
2. The β-1,4-glycosidic bonds cause adjacent monomers to alternate orientation, allowing chitin chains to lie flat and form straight, unbranched fibres.
3. Adjacent chitin chains form hydrogen bonds between their amino/acetyl groups, bundling into microfibrils that confer high tensile strength.
4. Chitin is insoluble and chemically stable, meaning it resists enzymatic degradation by most organisms, maintaining structural integrity of the exoskeleton or cell wall.

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-chitin-c4ab4769) · Published by Druglandscape Ltd.