Explain why viruses are not considered to be living cells, and describe how viruses reproduce inside a host organism.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Viruses infect a wide range of organisms, including bacteria, plants and animals. Scientists debate whether viruses should be classified as living or non-living.
Model answer (5 marks)
Viruses are not cells because they lack a cellular structure and are not composed of cells.
They cannot carry out life processes independently; they cannot respire, grow or reproduce on their own.
When a virus infects a host, it injects or inserts its DNA or RNA into the host cell.
The host cell’s machinery is then hijacked to produce and replicate new virus particles.
New virus particles are released, often destroying or bursting the host cell.
They cannot carry out life processes independently; they cannot respire, grow or reproduce on their own.
When a virus infects a host, it injects or inserts its DNA or RNA into the host cell.
The host cell’s machinery is then hijacked to produce and replicate new virus particles.
New virus particles are released, often destroying or bursting the host cell.
Examiner tips
- Use the exact phrases "do not have a cell structure" and "cannot carry out life processes independently" to hit the first two marks. Show the step‑by‑step infection cycle: injection of genetic material, use of host machinery, release of new virions. Remember to mention that the host cell may be destroyed or burst for the final mark.
Common mistakes
- Confusing viruses with bacteria and saying they are living organisms. Forgetting to state that viruses cannot respire or grow independently. Omitting the host cell’s role in producing new virions or the destruction of the host cell.
Mark scheme (5 marks)
- Viruses do not have a cell structure / are not made of cells
- Viruses cannot carry out life processes independently / cannot respire or grow on their own
- Viruses inject / insert their genetic material (DNA or RNA) into the host cell
- The host cell's machinery is used to produce / replicate new virus particles
- New virus particles are released (and the host cell may be destroyed / burst)
Key terms in this question
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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