IGCSE Biology glossary
Antibiotic
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A medicine that kills bacteria or prevents their reproduction without damaging human cells. Antibiotics such as penicillin are effective against bacterial infections but have no effect on viruses because viruses reproduce inside host cells.
What to include in an exam answer
Antibiotics do NOT work against viruses. This distinction is tested frequently. Also, overuse of antibiotics leads to antibiotic-resistant bacteria through natural selection.
Example in context
Explain why antibiotics are effective against bacteria but not viruses (2 marks): Antibiotics target bacterial cell processes such as cell wall formation. Viruses reproduce inside host cells using host machinery, so antibiotics cannot target them without harming the host cells.
Related syllabus topic
Diseases & immunity