Conceptual analysis
A leak in the mitochondrial membrane
- Unit 3
- 4 points
- About 10 minutes
You can use a calculator on this question, just like on exam day.
A short question about a biological system that gets disrupted. You describe and explain the normal process, then predict what the disruption causes and justify that prediction. On the exam: Question 4 of 6 in Section II; about 10 minutes suggested.
The question
In aerobic cellular respiration, the electron transport chain in the inner mitochondrial membrane creates a concentration gradient of hydrogen ions (H⁺), and ATP synthase uses this gradient to make ATP. Certain chemicals make the inner mitochondrial membrane leaky to H⁺, so H⁺ can cross the lipid bilayer directly instead of passing through ATP synthase. Researchers treat isolated mitochondria with one of these chemicals.
Suggested time: 10 minutes
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Part (a)
1 pointDescribe how the electron transport chain creates a concentration gradient of H⁺ across the inner mitochondrial membrane.
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Part (b)
1 pointExplain how ATP synthase uses the H⁺ gradient to make ATP.
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Part (c)
1 pointPredict the effect of the chemical on the rate of ATP production by ATP synthase in the treated mitochondria.
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Part (d)
1 pointJustify your prediction in part (c).
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