Antibiotics are medicines used to treat bacterial infections. Explain why antibiotics cannot be used to treat viral infections.

Eduqas GCSE Biology — 3.3 Treating, curing and preventing disease · 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 peptidoglycan cell wall or bacterial ribosomes.

Viruses lack these bacterial structures – they have no cell wall and their ribosomes are of a different type.

Instead of reproducing on their own, viruses replicate inside the host cell, using the host’s own machinery.

Because antibiotics target bacterial features, they would either be ineffective against viruses or would damage the host’s cells if they tried to act on viral components, making them unsuitable for viral infections.

Examiner tips

  • Use the word "target" to link antibiotics to bacterial structures; mention cell wall or ribosomes. Explain that viruses replicate inside host cells. Highlight that antibiotics would harm host cells if they tried to act on viruses.

Common mistakes

  • Claiming antibiotics work on viruses without explaining why. Forgetting to mention that viruses use host cell machinery. Using vague terms like "different" without specifying cell wall or ribosomes.

Mark scheme (4 marks)

  1. Antibiotics target/kill bacteria (or target bacterial cell structures/processes)
  2. Viruses do not have the same structures/processes as bacteria (e.g. no cell wall, no ribosomes of the same type)
  3. Viruses reproduce/replicate inside the host's own cells
  4. So antibiotics would damage/harm the host's cells if they targeted viruses / it is difficult to destroy viruses without harming the host

Key terms in this question

antibiotic

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