Question 51
FA scientist grew one strain of the gonorrhoea bacterium on an agar plate. She placed four paper discs on the plate. Three of the discs, P, Q and R, had each been soaked in a different antibiotic. The fourth disc, S, had been soaked in sterile water. The figure shows the plate after two days.
Figure: An agar plate covered with a lawn of gonorrhoea bacteria, showing four paper discs and the clear areas around them
a.[2]
Explain why disc S was placed on the plate.
b.[2]
Give the letter of the antibiotic that this strain of bacterium is resistant to. Explain your answer.
c.[2]
Describe how the scientist could use this plate to compare antibiotics P and Q quantitatively.
d.[1]
Give one variable that must be kept the same for this comparison to be valid.
3.1 Communicable diseases Questions
176 exam-style questions on AQA GCSE Biology 3.1 Communicable diseases, covering 3.1.1 Communicable (infectious) diseases, 3.1.2 Viral diseases, 3.1.3 Bacterial diseases, 3.1.4 Fungal diseases, 3.1.5 Protist diseases, 3.1.6 Human defence systems, 3.1.7 Vaccination, 3.1.8 Antibiotics and painkillers, and 3.1.9 Discovery and development of drugs. Each one has a worked solution and a mark scheme showing where the marks go.