Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologyeasymcq1 pt

During the reduction phase of the Calvin cycle, NADPH contributes mainly by...

A.splitting water molecules to release oxygen inside the stroma
B.activating rubisco so it can attach CO2 to RuBP
C.pumping protons across the thylakoid membrane to build a gradient
D.donating high-energy electrons that help convert 3-PGA into glyceraldehyde-3-phosphate

Explanation

Core Concept

After rubisco fixes CO2 into 3-PGA, each 3-PGA is first phosphorylated by ATP and then reduced by NADPH. NADPH delivers the electrons and a hydrogen ion that turn the carboxylic acid group of 3-PGA into the aldehyde sugar of G3P. This step stores light-derived chemical energy in a carbohydrate building block. NADP+ left behind returns to the light reactions for recharging.

Correct Answer

Ddonating high-energy electrons that help convert 3-PGA into glyceraldehyde-3-phosphate

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