Bacteria are cells; viruses are particles

By UK A Level Biology · independent study · myAudience

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Bacteria are cells; viruses are particles

Bacteria have cell membranes, cytoplasm and ribosomes but no membrane-bound nucleus. Many contain a circular chromosome and may carry plasmids. Their cell walls and other surface structures differ from those of plants and animals.

A virus has genetic material enclosed in a protein capsid, sometimes with an additional envelope. It does not have the cellular machinery needed for independent reproduction. Comparing a virus with a bacterial cell helps explain why treatments do not act on both in the same way.

In the bacterial model, peptidoglycan provides wall structure; optional capsules and flagella affect particular interactions or movement. Viral attachment proteins recognise compatible host-cell features, linking structure to host specificity. A virus may use DNA or RNA as genetic material; a capsid is a protein coat rather than a cell wall. The statement that a virus depends on cells concerns reproduction machinery, not a claim that its genetic information is absent.

Worked example: A particle contains RNA and a capsid but no ribosomes. Can it build its own proteins independently?

Protein synthesis requires ribosomes and additional cellular machinery.

The described particle lacks that machinery.

Answer: No; it must use suitable host-cell machinery.

Check your understanding: Does a bacterium lack DNA because it lacks a nucleus?

Answer: No.

Why: Its genetic material is present without a membrane-bound nuclear compartment.