SAT Subject Biology Practice Question 16: Answer and Explanation

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Question: 16

2. Which choice matches each description below to the correct stage of aerobic respiration?

I. Produces most of the ATP

II. Produces carbon dioxide (CO2)

III. Uses oxygen (O2)

A. I = chemiosmosis; II = electron transport chain; III = citric acid cycle
B. I = chemiosmosis; II = citric acid cycle; III = electron transport chain
C. I = citric acid cycle; II = chemiosmosis; III = electron transport chain
D. I = electron transport chain; II = chemiosmosis; III = citric acid cycle
E. I = electron transport chain; II = citric acid cycle; III = chemiosmosis

Correct Answer: B

Explanation:

The citric acid cycle breaks down glucose, producing carbon dioxide (II). The electron transport chain uses oxygen as a final electron acceptor (III). Most of the ATP in respiration (I) is produced by chemiosmosis, the movement of hydrogen ions down their concentration gradient to power ATP synthase.

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