A plant extract is dissolved in ethanol. A disc soaked in this solution produces a clear zone on a bacterial culture. A disc soaked in water produces no clear zone.
Which additional treatment is needed to determine whether the plant extract inhibits growth?
a matching disc containing the same volume of ethanol alone
a matching disc containing the same volume of extract solution
a larger disc containing the same volume of ethanol alone
a larger disc containing the same volume of extract solution
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.