Answers to AQA GCSE Testing Antiseptics, Antibiotics and Disinfectants (Biology)
Practice Question
1.When investigating how effective antibiotics are at controlling the population of bacteria, it is important to use uncontaminated cultures. Explain why.
This is to ensure that only the microorganisms under test are present.
2. Four different disinfectants were placed onto different paper discs. The paper discs were then placed onto the surface of agar as shown and incubated.
Use the diagram above to answer the following questions
2a. Which disinfectant was the most effective at killing the bacteria?
Disinfectant C
2b. Which Disinfectant was least effective at killing the bacteria?
Disinfectant D
3. Samantha measured the diameter of a clear zone on her agar dish. She found the value to be 2.5cm. Calculate the area of this clear zone.
Area of clear zone = πr2
Area of clear zone = 3.14 x 2.52
Area of clear zone = 19.6cm2