# Explain how the fluid mosaic model accounts for the lateral movement of membrane proteins and discuss why this movement is physiologically significant.

> IB DP Biology Higher Level (2023 syllabus) — B2.1 Membranes and membrane transport · Explain · 4 marks

## Mark scheme (4 marks)

1. The phospholipid bilayer is fluid / the hydrophobic tails are not rigidly fixed, allowing components to move laterally within each leaflet.
2. Membrane proteins (both integral/transmembrane and peripheral) are embedded within or associated with this fluid bilayer and are therefore free to diffuse laterally unless anchored to the cytoskeleton.
3. Lateral movement allows receptor proteins or transport proteins to cluster / redistribute, enabling cell signalling, formation of receptor complexes, or concentration of transporters at specific membrane domains (e.g. synaptic membrane, leading edge of a migrating cell).
4. Lateral movement also facilitates membrane repair and resealing after damage, as phospholipids and proteins can flow into disrupted regions, restoring bilayer integrity.

## Key terms

- [fluid mosaic model](https://www.gradenine.co.uk/glossary/fluid-mosaic-model)
- [lateral movement](https://www.gradenine.co.uk/glossary/lateral-movement)

## 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-fluid-mosaic-model-02b277fa) · Published by Druglandscape Ltd.