# Explain how the properties of phospholipids contribute to the formation of the first cell membranes during the origin of life.

> IB DP Biology Higher Level (2023 syllabus) — A2.1 Origins of cells · Explain · 4 marks

> A central challenge in the origin of life is explaining how a stable boundary could form spontaneously to separate an internal chemical environment from the surrounding aqueous medium.

## Mark scheme (4 marks)

1. Phospholipids are amphipathic / have both a hydrophilic phosphate head and hydrophobic fatty acid tails
2. In an aqueous environment, phospholipids spontaneously self-assemble into bilayers or vesicles to minimise contact of hydrophobic tails with water
3. Vesicle/liposome formation creates a compartment that separates an internal aqueous environment from the external medium, providing a proto-cell boundary
4. This compartmentalisation would have allowed concentrations of organic molecules / early catalytic RNA / metabolic reactions to be maintained inside, increasing the probability of the emergence of life

## Key terms

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

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-properties-of-phospholipids-b0560684) · Published by Druglandscape Ltd.