A drug is defined as a substance that alters the body's chemical reactions when introduced into the body. Describe how antibiotics work against bacterial infections and explain why a doctor would not prescribe antibiotics to treat a viral infection such as influenza.

Cambridge International IGCSE Biology (0610) — 15.1 Drugs · Describe and 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 kill bacteria or prevent their growth.

Some antibiotics destroy the bacterial cell wall, causing the cell to burst.

Viruses do not have a cell wall (or the same cellular structure as bacteria).

Because viruses do not reproduce or grow in the same way as bacteria, antibiotics have no effect on them.

Examiner tips

  • Use the exact phrases "kill bacteria" and "prevent/inhibit growth". Mention the cell‑wall mechanism. State that viruses lack a cell wall. Explain that antibiotics target bacterial growth, not viral replication.

Common mistakes

  • Confusing antibiotics with antiviral drugs. Saying antibiotics treat viruses. Omitting the cell‑wall detail or the reason viruses are unaffected.

Mark scheme (4 marks)

  1. Antibiotics kill bacteria OR prevent/inhibit the growth of bacteria
  2. Some antibiotics work by destroying the bacterial cell wall, causing the cell to burst
  3. Viruses do not have a cell wall (or the same cellular structure as bacteria)
  4. Viruses do not reproduce/grow in the same way as bacteria, so antibiotics have no effect on them

Key terms in this question

antibiotic · drug · bacteria

Related

More Drugs questions

▶ Try answering this question with AI marking (free) →