A slide of potato cells was viewed using a light microscope - Edexcel - GCSE Biology - Question 9 - 2020 - Paper 1
Question 9
A slide of potato cells was viewed using a light microscope.
Figure 20 is a drawing of the slide showing starch grains in the potato cells.
Calculate the mean numb... show full transcript
Worked Solution & Example Answer:A slide of potato cells was viewed using a light microscope - Edexcel - GCSE Biology - Question 9 - 2020 - Paper 1
Step 1
Calculate the mean number of starch grains in potato cells P, Q and R.
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Answer
To find the mean number of starch grains in cells P, Q, and R, we first need to count the number of starch grains in each cell. Let's assume:
Cell P has 6 starch grains
Cell Q has 6 starch grains
Cell R has 6 starch grains
Adding these together gives us:
6+6+6=18
Now, divide the total by the number of cells (3):
Mean=318=6
Thus, the mean number of starch grains is 6.
Step 2
Which structures are found in plant cells but are not found in animal cells?
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Answer
The correct answer is B: cell wall, cell membrane, cytoplasm. Plant cells are characterized by structures that are not present in animal cells, such as cell walls and chloroplasts.
Step 3
Calculate the percentage difference in the mean length of starch grains in potato 2 at 5 weeks and in potato 3 at 10 weeks.
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Answer
To calculate the percentage difference:
Identify the mean lengths:
Potato 2 (5 weeks): 50 µm
Potato 3 (10 weeks): 30 µm
Use the formula for percentage difference:
Percentage Difference=Value2(Value2−Value3)×100
Substitute the values:
Percentage Difference=50(50−30)×100=5020×100=40%
Therefore, the percentage difference is 40%.
Step 4
State two variables the scientist should have controlled to improve this investigation.
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Answer
Variety of potato used
Temperature during the storage of potatoes
Step 5
State why the potatoes need glucose.
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Answer
Potatoes need glucose for energy and respiration. Glucose is a key product of photosynthesis and is utilized in cellular processes to produce ATP, which is essential for growth and maintenance.
Step 6
Devise a plan to investigate the effect of light intensity on the rate of photosynthesis.
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Answer
To investigate the effect of light intensity on the rate of photosynthesis, follow this plan:
Setup: Place pondweed in a beaker filled with water and a source of light at varying distances.
Control Variables: Ensure constant conditions for temperature, type of pondweed, and amount of water.
Measurement: Measure the number of oxygen bubbles released over a fixed time as an indicator of photosynthesis rate.
Repeat: Perform the experiment at different light intensities by changing the distance of the light source and record the results.
Data Analysis: Compare the rates of photosynthesis obtained from different light intensities to draw conclusions.
