GCSE Biology · Edexcel 1BI0 · Topic 5D
Antibiotics and new medicines
Key points
- Antibiotics kill bacteria or stop them growing but have no effect on viruses. Overuse leads to antibiotic-resistant strains.
- Core practical: grow bacteria on agar plates with antiseptic or antibiotic discs; measure the clear zone (zone of inhibition). Area of a circle: .
- Use aseptic technique: sterilise equipment, work near a flame, tape the lid without fully sealing it and incubate at 25 °C to avoid growing harmful bacteria.
- New medicines go through discovery, development and preclinical testing on cells, tissues and animals.
- Clinical trials: first low doses in healthy volunteers (safety), then patients (effectiveness and best dose). Double-blind trials and placebos reduce bias.
- Tests check that a drug is safe (toxicity), works (efficacy) and the right dosage.
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Antibiotics transformed medicine, but they only work against bacteria and their overuse is breeding resistant strains. This sub-topic covers how antibiotics and antiseptics are tested in the lab and how a new medicine gets from discovery to…
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