A student investigated the antibiotic properties of garlic - Edexcel - GCSE Biology - Question 5 - 2023 - Paper 1
Question 5
A student investigated the antibiotic properties of garlic.
Bacteria were spread on an agar plate.
A paper disc was soaked in garlic extract and placed on this agar ... show full transcript
Worked Solution & Example Answer:A student investigated the antibiotic properties of garlic - Edexcel - GCSE Biology - Question 5 - 2023 - Paper 1
Step 1
Suggest why there is an area with no bacterial growth.
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Answer
The area with no bacterial growth is likely due to the antibacterial properties of garlic. The garlic extract soaked into the paper disc kills the bacteria in its vicinity, thus creating a clear zone around the disc where no bacterial growth occurs.
Step 2
Explain which agar plate, shown in Figure 10, has the paper disc containing the 100 mg/cm² garlic extract.
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Answer
Agar plate C has the paper disc containing the 100 mg/cm² garlic extract, as it shows the largest area with no bacterial growth compared to agar plates A and B, which contain lower concentrations of garlic extract.
Step 3
Give one way the student could improve their results.
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The student could improve their results by using a control experiment that uses agar plates without garlic extract to compare against the plates with the extract.
Step 4
Calculate the area with no bacterial growth for agar plate B.
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To calculate the area of a circle, use the formula:
ext{π} r^2$$
Given that the radius (r) is 5 mm and using π = 3.14:
$$ ext{Area} = 3.14 imes (5)^2 = 3.14 imes 25 = 78.5 ext{ mm}^2$$
Step 5
State the reason for heating the spreader in the flame of a Bunsen burner before use.
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The spreader is heated in the flame to sterilize it and kill any bacteria or microorganisms that may be present, preventing contamination of the agar plate.
Step 6
Give two other ways of working safely with microorganisms.
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Disinfect the work surface before and after the experiment to eliminate any potential contamination.
Wear protective gloves and a mask to minimize exposure to harmful microorganisms.
