# Explain how a virus with a lipid envelope acquires that envelope and why its presence affects the ability of the immune system to recognise and neutralise the virus.

> IB DP Biology Higher Level (2023 syllabus) — A2.3 Viruses (HL only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Enveloped viruses acquire their lipid envelope from the host cell's membrane (plasma membrane or nuclear envelope / endoplasmic reticulum membrane) during budding.
2. Viral glycoproteins (encoded by the viral genome) are inserted into the host membrane before budding, and these become embedded in the envelope.
3. Because the envelope's lipid bilayer is host-derived, the immune system may not recognise it as foreign / it resembles the host's own membranes, reducing immune detection.
4. Antibodies (and other immune effectors) must target the viral glycoproteins on the envelope surface to neutralise the virus; if these glycoproteins change (antigenic variation) or are sparse, neutralisation is less effective.

## Key terms

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

## 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-a-virus-with-a-a81ef3fb) · Published by Druglandscape Ltd.