Infection & ResponseRequired Practical

Required Practical: Investigating Antibiotic Action

Part of Antibiotics and Drug Resistance — GCSE Biology

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.

Topic position

Section 4 of 18

Practice

20 questions

Recall

24 flashcards

🧪 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

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.