# Explain how fibrous proteins differ from globular proteins in terms of their structure and function.

> IB DP Biology Higher Level (2023 syllabus) — B1.2 Proteins · Explain · 4 marks

## Mark scheme (4 marks)

1. Fibrous proteins have a repetitive, elongated/extended polypeptide structure (e.g. alpha-helix or beta-sheet repeated along an axis), whereas globular proteins are folded into a compact, roughly spherical tertiary structure.
2. Fibrous proteins are generally insoluble in water, while globular proteins are generally water-soluble due to hydrophilic R-groups on their surface.
3. Fibrous proteins serve structural/mechanical roles (e.g. collagen in connective tissue, keratin in hair/nails), providing strength and support.
4. Globular proteins have dynamic/metabolic functions such as catalysis (enzymes), transport (haemoglobin), or cell signalling (hormones/receptors), made possible by their specific active site or binding site formed through tertiary folding.

## Key terms

- [fibrous protein](https://www.gradenine.co.uk/glossary/fibrous-protein)
- [globular protein](https://www.gradenine.co.uk/glossary/globular-protein)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-fibrous-proteins-differ-from-bc7b937a) · Published by Druglandscape Ltd.