Question 1
Unit 2 style
Which precaution during Core practical 9 helps to prevent contamination of a bacterial culture?
- Sealing the Petri dish completely with tape
- Flaming the neck of the culture bottle after opening it
- Incubating the dish at 37 °C
- Leaving the lid of the dish off while spreading the bacteria
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Question 2
Unit 2 style
State three conditions that bacteria need for growth.
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Question 3
Unit 2 style
Explain why aseptic technique is used when handling bacteria.
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Question 4
Unit 3 style
A student wants to compare the antimicrobial effect of extracts from three plants on a non-pathogenic bacterium. Describe a method that the student could use, including the control variables and how the results should be processed.
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Question 5
Unit 3 style
A student placed discs soaked in three plant extracts and one disc soaked in solvent only on a bacterial lawn, then measured the clear zone around each disc. The table shows the mean diameter of each zone. Calculate the area of the clear zone for extract B and state which extract was the most effective.
| Disc | Mean diameter of clear zone (mm) |
|---|---|
| Extract A | 14 |
| Extract B | 9 |
| Extract C | 6 |
| Solvent only | 0 |
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Question 6
Unit 2 style
Suggest why chemicals from plants may be useful as new medicines.
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Question 7
Unit 2 style
Explain the importance of using a placebo and a double-blind design in a drug trial.
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Question 8
Unit 2 style
William Withering used a herbal mixture to treat dropsy in the 18th century. Compare and contrast his approach with modern drug testing.