A microbiologist investigated the antimicrobial effectiveness of three different plant extracts—Tea tree oil (T), Eucalyptus oil (E), and Thyme oil (H)—against a strain of Staphylococcus aureus cultured on an agar plate.

After incubation, the researcher measured the diameter of the circular zone of inhibition (the clear zone where no bacteria grew) around each extract-soaked paper disc:

Plant extract T: $mm18\text{ mm}$
Plant extract E: $mm28\text{ mm}$
Plant extract H: $mm14\text{ mm}$

Describe one aseptic technique the researcher should have used to prevent contamination of the agar plate when preparing this experiment.

Which plant extract is the most effective? Give a reason for your answer.

Calculate the area of the zone of inhibition for plant extract E. Use $π=3.14\pi = 3.14$ . Give your answer to 1 decimal place and include the unit in your final answer.

Suggest one way the researcher could improve the reliability of this investigation.

After incubation, the researcher measured the diameter of the circular zone of inhibition (the clear zone where no bacteria grew) around each extract-soaked paper disc:

Plant extract T: $mm18\text{ mm}$
Plant extract E: $mm28\text{ mm}$
Plant extract H: $mm14\text{ mm}$

Describe one aseptic technique the researcher should have used to prevent contamination of the agar plate when preparing this experiment.

Which plant extract is the most effective? Give a reason for your answer.

Calculate the area of the zone of inhibition for plant extract E. Use $π=3.14\pi = 3.14$ . Give your answer to 1 decimal place and include the unit in your final answer.

Suggest one way the researcher could improve the reliability of this investigation.

1.1 Cell structure

Question 58

Markscheme

1.1 Cell structure

Question 58

Markscheme

1.1 Cell structure

Question 58

1.1 Cell structure Questions

1.1 Cell structure

Question 58

1.1 Cell structure Questions