# Explain how the formation of different levels of protein structure is responsible for the specific shape and function of a named fibrous protein.

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

## Mark scheme (4 marks)

1. Names a specific fibrous protein (e.g. collagen, keratin, elastin, fibrin)
2. Primary structure (sequence of amino acids/peptide bonds) determines which interactions are possible at higher levels of organisation
3. Secondary structure forms through hydrogen bonding between peptide/backbone groups, creating repeating motifs (e.g. alpha-helix or beta-pleated sheet) that give the protein its extended/regular shape
4. Quaternary structure / further assembly (e.g. coiling of helices, cross-linking) gives the fibrous protein its mechanical properties (strength, flexibility, inextensibility) suited to its function

## Key terms

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

## 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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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-formation-of-different-83cb9027) · Published by Druglandscape Ltd.