A biology student investigated the antimicrobial properties of three different plant extracts, labeled A, B, and C, against Escherichia coli bacteria grown on an agar plate. After incubating the plate at 25∘C25^\circ\text{C}25∘C for 48 hours, the student observed the results shown below.
Describe two aseptic techniques the student should have used when preparing and setting up the agar plate.
Which plant extract is the most effective? Give a reason for your answer.
Calculate the area where no bacteria were growing for plant extract A. The diameter of the zone of inhibition for plant extract A is measured to be 2.8 cm. Use π=3.14\pi = 3.14π=3.14. Give the unit.
Suggest one way the student could improve this investigation.
Cell structure Questions
Practise AQA GCSE Biology Cell structure with exam-style questions for Foundation and Higher tier. 51 questions covering Eukaryotes and prokaryotes, Animal and plant cells, Cell specialisation, Cell differentiation, Microscopy, and Culturing microorganisms (biology only), matched to the AQA GCSE Biology (8461) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.