Antibiotics explains how a specific barrier, pathogen interaction, immune mechanism, treatment response or population process contributes to protection against infectious disease.
Coverage 2016–2025 · Updated 16 Jul 2026
Antibiotics are chemicals that block processes in bacteria while having little or no effect on corresponding processes in eukaryotic host cells.
Selective targets include bacterial cell-wall synthesis or bacterial ribosomes. Human cells lack bacterial walls and their cytoplasmic ribosomes differ, allowing a susceptible bacterial infection to be treated without the same target effect on human cells.
Identify bacterial target → explain disrupted bacterial process → explain why eukaryotic cells lack or differ in that target → predict treatment only for susceptible bacteria.
An antibiotic that blocks bacterial peptidoglycan-wall synthesis can stop dividing bacteria, while human cells have no peptidoglycan wall to block.
Viruses have no bacterial cell wall, ribosome or independent bacterial metabolism; they replicate using host-cell machinery. Antibiotics therefore do not control viral infections.
This objective is assessed through structured response, commonly using Explain / Outline / Identify.
Explain / Outline / Identify / Distinguish / Suggest
Mark schemes repeatedly reward named details, correct sequence and clear distinctions between similar processes.
Explaining antibiotic action as antibody stimulation instead of inhibition of bacterial processes.
Representative question
(i) Estimate the diameter of the zone of inhibition of chloramphenicol.
(ii) Distinguish between the action of tetracycline and penicillin on B. subtilis.
(iii) Suggest a reason for the result with disc X .
