1.1 Cell structure

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

Question 3

Medium35%

A student investigated the antimicrobial effectiveness of three different disinfectants, labeled P, Q, and R, against a specific strain of bacterium growing on a nutrient agar plate. After incubating the plate at $25∘C25^\circ\text{C}$ for 48 hours, the results shown below were observed.

A Petri dish containing nutrient agar seeded with a bacterium. Three paper discs containing different disinfectants, labeled P, Q, and R, are placed on the agar. Around P, there is a very large clear circular zone (zone of inhibition). Around Q, there is a medium-sized clear circular zone. Around R, there is a very small clear circular zone.

Describe two aseptic techniques the student should have used when preparing and setting up the agar plate.

[2]

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

[1]

Calculate the area where no bacteria were growing for disinfectant P. The diameter of the zone of inhibition for disinfectant P is measured to be 2.8 cm. Use $π=3.14\pi = 3.14$ . Give the unit.

[5]

Suggest one way the student could improve this investigation.

[3]

1.1 Cell structure

Question 3

1.1 Cell structure Questions

1.1 Cell structure

Question 3

1.1 Cell structure Questions