This required practical covers Required Practical: Investigating Antibiotic Action within Antibiotics and Drug Resistance for GCSE Biology. Antibiotic function, bacterial resistance evolution, responsible use, global health impact It is section 4 of 18 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
🧪 Required Practical: Investigating Antibiotic Action
Disc Diffusion Method
Aim: To investigate the effectiveness of different antibiotics against bacterial growth
Method:
- Prepare sterile agar plates
- Spread bacterial culture evenly across the plate
- Place antibiotic discs on the surface
- Incubate at 25°C for 24-48 hours
- Measure zones of inhibition around each disc
Results Interpretation:
- Large zone: Antibiotic is very effective
- Small zone: Antibiotic has limited effectiveness
- No zone: Bacteria are resistant to the antibiotic
Aseptic Techniques:
- Work near a Bunsen burner flame for sterile updraft
- Flame bottle necks before and after use
- Use sterile equipment (autoclave sterilization)
- Handle petri dish lids carefully - don't lift fully
- Seal plates with tape after inoculation
Practice questions for Antibiotics and Drug Resistance
What do antibiotics kill or stop growing?
Explain how antibiotic resistance develops in bacteria through natural selection. (3 marks)
Quick recall flashcards
What are antibiotics and what do they target?
Antibiotics are chemicals that kill bacteria or stop them from growing.
They target structures that bacteria have but human cells do not, such as cell walls.
Examples: penicillin, amoxicillin, streptomycin.
Why do antibiotics NOT work against viruses?
Antibiotics target bacterial cell walls and bacterial processes.
Viruses do not have cell walls and use the host cell's own machinery to reproduce.
There is nothing for the antibiotic to target in a virus.