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A slide of potato cells was viewed using a light microscope - Edexcel - GCSE Biology - Question 3 - 2020 - Paper 1
Question 3
A slide of potato cells was viewed using a light microscope. Figure 4 is a drawing of the slide showing starch grains in the potato cells. (a) (i) Calculate the mea... show full transcript
Worked Solution & Example Answer:A slide of potato cells was viewed using a light microscope - Edexcel - GCSE Biology - Question 3 - 2020 - Paper 1
Step 1
Calculate the mean number of starch grains in potato cells P, Q and R.
Answer
To calculate the mean number of starch grains in potato cells P, Q, and R, sum the number of starch grains observed in each cell and then divide by the number of cells.
For example, if P has 6 grains, Q has 5 grains, and R has 7 grains, the calculation would be:
ext{Mean} = rac{(6 + 5 + 7)}{3} = rac{18}{3} = 6.
Thus, the mean number of starch grains is 6.
Step 2
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.
Answer
From Figure 6, the mean length of starch grains in potato 2 after 5 weeks is 64 µm, and in potato 3 after 10 weeks, it is 30 µm.
The percentage difference can be calculated using the formula:
ext{Percentage difference} = rac{ ext{new value - old value}}{ ext{old value}} imes 100
Substituting the values:
ext{Percentage difference} = rac{30 - 64}{64} imes 100 = rac{-34}{64} imes 100 = -53.125
Thus, the percentage difference is approximately 53.1% decrease.
Step 4
Step 5
Step 6
Describe how starch is broken down into glucose.
Answer
Starch is broken down into glucose through the action of enzymes, such as amylase. The process involves:
- Enzymes catalyzing the hydrolysis of the starch molecules into smaller glucose units.
- The bonds between glucose molecules in starch are broken to release individual glucose monomers.