Explain why antibiotics cannot be used to treat diseases caused by viruses.

WJEC GCSE Biology (Wales) — 2.6.3 Medicines and drugs · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Antibiotics act on structures or processes that are unique to bacteria, such as the bacterial cell wall, ribosomes or DNA replication machinery. Viruses lack these bacterial targets – they are not living cells and have no cell wall or ribosomes. Instead, viruses hijack the host cell’s machinery to replicate. Because antibiotics cannot affect the host cell processes that viruses use, they are ineffective against viral infections. Antiviral drugs, which interfere with viral replication, are therefore used instead.

Examiner tips

Use the word ‘target’ to show why antibiotics fail; mention the lack of a cell wall or ribosomes in viruses; explain that viruses replicate inside host cells; note that antivirals are the alternative treatment.
Structure your answer in four clear points matching the mark scheme.
Use UK spelling and precise terminology (e.g. ‘cell wall’, ‘ribosomes’, ‘replicate’).

Common mistakes

Confusing antibiotics with antivirals; claiming antibiotics kill viruses.
Forgetting that viruses lack a cell wall or ribosomes; or that they replicate inside host cells.
Using vague language such as ‘viruses are different’ without explaining the mechanism.

Mark scheme (4 marks)

Antibiotics target/kill bacteria (not viruses)
Viruses are not living cells / viruses do not have a cell structure that antibiotics can target
Viruses reproduce/replicate inside the host's own cells
Antiviral drugs are used instead (to treat viral diseases)

Key terms in this question

antibiotic · virus