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Describe how a sample of chloroplasts could be isolated from leaves - AQA - A-Level Biology - Question 5 - 2021 - Paper 1
Question 5
Describe how a sample of chloroplasts could be isolated from leaves. Scientists grew two groups of plants: - control plants with all the inorganic ions needed - iro... show full transcript
Worked Solution & Example Answer:Describe how a sample of chloroplasts could be isolated from leaves - AQA - A-Level Biology - Question 5 - 2021 - Paper 1
Step 1
Describe how a sample of chloroplasts could be isolated from leaves.
Answer
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The first step in isolating chloroplasts is to break open the cells or tissues of the leaves. This can be accomplished by grinding or blending the leaves with a cold, buffered solution to maintain osmotic balance and prevent degradation.
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Next, the mixture is filtered to remove larger pieces of leaf debris, leaving the cell organelles suspended in the solution.
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The solution is then centrifuged, allowing the heavier organelles, including chloroplasts, to settle at the bottom of the tube while lighter materials remain in the supernatant.
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By repeating the centrifugation at different speeds, you can further purify the chloroplasts, which will sediment more rapidly than other organelles.
Step 2
Step 3
Step 4
The ratio of protein to chlorophyll in iron-deficient plants.
Answer
The protein to chlorophyll ratio in control plants is 9:1. Given that the mass of protein is 40% of control and the mass of chlorophyll is 10% of control in iron-deficient plants, the ratio can be calculated.
Calculating the Iron-Deficient Plants Ratio:
Using the same proportion of protein to chlorophyll as the control, the ratio in iron-deficient plants is:
ext{Ratio} = rac{40 ext{%}}{10 ext{%}} = 4:1
Step 5
Use Figure 6 to suggest why iron-deficient plants have a reduced growth rate.
Answer
Iron-deficient plants typically exhibit reduced chlorophyll content, as shown in Figure 6. This decrease in chlorophyll leads to less efficient photosynthesis, resulting in lower energy production. Consequently, the plants may struggle to grow properly due to insufficient energy and resources.