A slide of potato cells was viewed using a light microscope - Edexcel - GCSE Biology Combined Science - Question 2 - 2020 - Paper 1
Question 2
A slide of potato cells was viewed using a light microscope.
Figure 3 is a drawing of the slide showing starch grains in the potato cells.
(a) (i) Calculate the me... show full transcript
Worked Solution & Example Answer:A slide of potato cells was viewed using a light microscope - Edexcel - GCSE Biology Combined Science - Question 2 - 2020 - Paper 1
Step 1
(a) (i) Calculate the mean number of starch grains in potato cells P, Q and R.
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Answer
To calculate the mean number of starch grains, count the number of starch grains in each cell:
Cell P: 10 grains
Cell Q: 8 grains
Cell R: 12 grains
Total = 10 + 8 + 12 = 30 grains.
Mean = Total grains / Number of cells = 30 / 3 = 10 grains.
Step 2
(a) (ii) Which structures are found in plant cells but are not found in animal cells?
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Answer
The correct answer is D: cell wall, chloroplast, large vacuole. These structures are characteristic of plant cells and serve specific functions that support plant biology.
Step 3
(b) (i) 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
Mean length of starch grains in potato 2 at 5 weeks = 50 μm.
Mean length of starch grains in potato 3 at 10 weeks = 30 μm.
Percentage difference = ( \frac{(50 - 30)}{50} \times 100 = 40% )
Step 4
(b) (ii) State two variables the scientist should have controlled to improve this investigation.
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Answer
Temperature at which the potatoes were stored;
Quality of light exposure before storage.
Step 5
(b) (iii) State why the potatoes need glucose.
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The potatoes need glucose for energy during respiration. Glucose is a crucial source of energy that supports various metabolic processes.
Step 6
(b) (iv) Describe how starch is broken down into glucose.
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Starch is broken down into glucose by the action of enzymes such as amylase, which catalyze the hydrolysis of starch. During this process, starch molecules fit into the active site of the enzyme, leading to the breaking of bonds between glucose molecules, resulting in the conversion of starch into simpler glucose monomers.
