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Each colony starts as one bacterium - Edexcel - GCSE Biology - Question 3 - 2023 - Paper 1
Question 3
Each colony starts as one bacterium. Every time bacteria reproduce, the number of bacteria in each colony doubles. (a) Calculate the number of bacteria in a colony... show full transcript
Worked Solution & Example Answer:Each colony starts as one bacterium - Edexcel - GCSE Biology - Question 3 - 2023 - Paper 1
Step 1
Calculate the number of bacteria in a colony after five hours
Answer
To determine the number of bacteria after five hours, we first convert the time into the number of 30-minute intervals within five hours.
Five hours is equal to 300 minutes. Therefore:
Number of intervals = ( \frac{300 \text{ minutes}}{30 \text{ minutes}} = 10 ) intervals.
Since the number of bacteria doubles with each interval, we can express the total number of bacteria after 10 intervals as:
( N = N_0 \times 2^n )
Where:
- ( N_0 ) is the initial amount (1 bacterium),
- ( n ) is the number of reproduction cycles (10).
Thus,( N = 1 \times 2^{10} = 1024 ).
The colony will contain 1024 bacteria after five hours.
Step 2
Explain why antibiotics can be used to treat bacterial infections
Answer
Antibiotics are effective against bacterial infections because they target specific features of bacterial cells or their life processes.
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Mechanism of Action: Antibiotics can inhibit cell wall synthesis, disrupt protein synthesis, or interfere with nucleic acid synthesis, which are crucial processes for bacterial growth and reproduction.
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Selective Toxicity: Antibiotics generally harm bacteria without affecting human cells, due to differences in cellular structures and functions.
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Limited Resistance: While some bacteria can develop resistance to antibiotics, many remain susceptible, making antibiotics a powerful tool in combating infections.
Step 3
Calculate the magnification of this drawing
Answer
To calculate the magnification of the drawing, use the formula:
( \text{Magnification} = \frac{\text{Size of drawing}}{\text{Actual size}} )
In this case, the size of the drawing is 80 mm and the actual size of the bacterium is 0.005 mm. Thus:
( \text{Magnification} = \frac{80 \text{ mm}}{0.005 \text{ mm}} = 16000 )
Therefore, the magnification of the drawing is 16,000 times.