# Explain how proteins are able to carry out such a diverse range of functions within living organisms.

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

> Proteins are the most structurally diverse biological macromolecules, performing roles including catalysis, transport, defence, and structural support.

## Mark scheme (4 marks)

1. There are 20 different amino acids that can be combined in any sequence, giving an enormous variety of possible polypeptides.
2. The unique sequence of amino acids determines the specific tertiary / three-dimensional structure of each protein through interactions between R groups.
3. The specific three-dimensional shape of a protein determines its function, as it allows the protein to interact precisely with other molecules (e.g. substrate, receptor, antigen).
4. Proteins can also be fibrous or globular, and can be formed from multiple polypeptide subunits (quaternary structure), extending the range of possible structures and functions.

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-proteins-are-able-to-f4ac3deb) · Published by Druglandscape Ltd.