SAT Subject Biology Practice Question 16: Answer and Explanation
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
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.