Equal volumes of two antibiotics at the same concentration are placed on identical discs on a bacterial culture. Antibiotic P produces a larger clear zone than antibiotic Q. P also diffuses through agar faster than Q.
Which conclusion is justified?
P inhibited growth over a larger area, but diffusion affects the comparison.
P killed more bacteria at every concentration, because its zone was larger.
Q killed no bacteria in the culture, because its zone was smaller.
Q would be less effective in patients, because its diffusion was slower.
45 exam-style questions on Edexcel GCSE Biology 5.3 Immune system and medicines, covering 5.3.1 The specific immune system, 5.3.2 Response to immunisation, 5.3.3 Advantages and disadvantages of immunisation, 5.3.4 Antibiotics and bacterial infections, 5.3.5 Aseptic techniques in culturing, 5.3.6 Cross-sectional areas of cultures, 5.3.7 Stages of developing new medicines, and 5.3.8 Production of monoclonal antibodies. Each one has a worked solution and a mark scheme showing where the marks go.