The three stages of the Calvin cycle are A) (1) fix CO₂, (2) make a C₃ sugar, and (3) make glucose. B) (1) fix CO₂, (2) use NADPH and ATP, and (3) regenerate the starting C₅ molecule. C) (1) use ATP, NADPH, and CO₂, (2) make a C₃ molecule, and (3) regenerate the starting C₃ molecule. D) (1) use a C₅ sugar, (2) reduce CO₂ with NADPH, and (3) use ATP to regenerate the starting C₅ molecule.

Question

Quizplus · Accepted Answer

The three stages of the Calvin cycle are:
(1) Fixation: CO2 combines with ribulose-1,5-bisphosphate (RuBP) to form two molecules of 3-phosphoglycerate (3-PGA) using the enzyme RuBisCO.
(2) Reduction: ATP and NADPH are used to convert 3-PGA into glyceraldehyde-3-phosphate (G3P), which can be used to make glucose or regenerated back into RuBP.
(3) Regeneration: Some G3P molecules are used to regenerate the starting molecule RuBP, which is needed for the fixation step to continue.

Option B describes the different stages of the Calvin cycle accurately.

The Three Stages of the Calvin Cycle Are