Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologymediummcq1 pt

Within the Calvin cycle, ATP and NADPH delivered from the light-dependent reactions fill different jobs. Which assignment is correct?

A.NADPH phosphorylates sugars while ATP donates electrons to growing carbon chains
B.Both molecules are consumed solely to split water at photosystem II
C.ATP phosphorylates cycle intermediates while NADPH donates the electrons that truly reduce them toward carbohydrate
D.Each molecule becomes permanently built into the growing carbon skeleton of the sugar

Explanation

Core Concept

The reduction phase separates the two currencies cleanly. ATP first converts 3-phosphoglycerate into 1,3-bisphosphoglycerate and later helps regenerate RuBP, contributing energy but no electrons. NADPH then delivers a hydride equivalent to that activated intermediate, turning an acid into the aldehyde glyceraldehyde 3-phosphate. Electron addition is reduction in action, so NADPH supplies the actual reducing power while ATP foots the energy bill.

Correct Answer

CATP phosphorylates cycle intermediates while NADPH donates the electrons that truly reduce them toward carbohydrate

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