Dual Enrollment Biology Practice Test

Which statement correctly describes the two stages of photosynthesis and their outputs?

Light-dependent reactions produce ATP, NADPH, and O2; the Calvin cycle uses ATP and NADPH to fix CO2 into triose phosphates Light-dependent reactions fix CO2 into sugars; the Calvin cycle produces ATP Light-dependent reactions release CO2; the Calvin cycle releases O2 Light-dependent reactions produce glucose directly; the Calvin cycle releases O2

Correct Answer:

Light-dependent reactions produce ATP, NADPH, and O2; the Calvin cycle uses ATP and NADPH to fix CO2 into triose phosphates

Explanation:

Photosynthesis has two linked stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, energy from light drives the splitting of water, releasing oxygen, and generates ATP and NADPH as energy carriers. In the Calvin cycle, ATP and NADPH power the fixation of carbon dioxide into triose phosphates, which are later used to synthesize sugars such as glucose. So the statement that correctly describes both stages is that the light-dependent reactions produce ATP, NADPH, and O2, while the Calvin cycle uses those energy carriers to fix CO2 into sugars. The other descriptions mix up which stage does CO2 fixation, which stage produces ATP, and what each stage releases, leading to incorrect roles and outputs.

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