# Explain how the lytic cycle of a bacteriophage results in the release of new phage particles from a host bacterial cell.

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

## Mark scheme (4 marks)

1. The bacteriophage injects its nucleic acid (DNA) into the host bacterium, whilst the protein capsid remains outside.
2. The host cell's ribosomes and metabolic machinery are hijacked / used to transcribe and translate viral genes, producing phage proteins (including capsid proteins) and replicating phage DNA.
3. New phage particles are assembled (self-assembly of capsid proteins around replicated phage DNA) inside the host cell.
4. Phage-encoded lysozyme (or equivalent lytic enzyme) breaks down the bacterial cell wall, causing lysis and release of hundreds of new phage particles.

## Key terms

- [lytic cycle](https://www.gradenine.co.uk/glossary/lytic-cycle)
- [bacteriophage](https://www.gradenine.co.uk/glossary/bacteriophage)

## 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-lytic-cycle-of-133f2677) · Published by Druglandscape Ltd.