Infection & ResponseTopic Summary
Knowledge Organiser
Part of Antibiotics and Drug Resistance — GCSE Biology
This topic summary covers Knowledge Organiser within Antibiotics and Drug Resistance for GCSE Biology. Antibiotic function, bacterial resistance evolution, responsible use, global health impact It is section 18 of 19 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 18 of 19
Practice
20 questions
Recall
24 flashcards
Knowledge Organiser
Natural Selection Steps
- Random mutation gives resistance to one bacterium
- Antibiotic = selection pressure
- Non-resistant bacteria killed
- Resistant bacteria survive and reproduce
- Offspring inherit resistance gene
- Resistant strain becomes dominant
How Antibiotics Work
- Penicillin: blocks cell wall synthesis → cell bursts
- Streptomycin: blocks bacterial ribosomes → no protein synthesis
- Only affect bacteria — viruses have no cell wall or bacterial ribosomes
- MRSA: resistant to methicillin + many others
- Disc diffusion: larger zone = more effective
Common Marks Lost
- "Person becomes resistant" — bacteria become resistant, not people
- "Bacteria learn" — random mutation, not deliberate adaptation
- Missing "mutation" in natural selection answers
- Not explaining WHY completing course reduces resistance
- Saying antibiotics kill viruses (they do not)