AP BIOLOGY

PHOTOSYNTHESIS

THE CALVIN CYCLE

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What is the second stage of the Calvin Cycle?
A
Carbon fixation
B
Reduction
C
Regeneration of RUBP
D
Secondary
Explanation: 

Detailed explanation-1: -Reduction. In the second stage, ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon sugar, glyceraldehyde-3-phosphate (G3P). This stage gets its name because NADPH donates electrons to, or reduces, a three-carbon intermediate to make G3P.

Detailed explanation-2: -Reduction. It is the second stage of Calvin cycle. The 3-PGA molecules created through carbon fixation are converted into molecules of simple sugar – glucose. This stage obtains energy from ATP and NADPH formed during the light-dependent reactions of photosynthesis.

Detailed explanation-3: -Figure: The Calvin Cycle: The Calvin cycle has three stages. In stage 1, the enzyme RuBisCO incorporates carbon dioxide into an organic molecule, 3-PGA. In stage 2, the organic molecule is reduced using electrons supplied by NADPH.

Detailed explanation-4: -The Calvin cycle has three stages. In stage 1, the enzyme RuBisCO incorporates carbon dioxide into an organic molecule. In stage 2, the organic molecule is reduced. In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue.

Detailed explanation-5: -The energy from the ATP and NADPH is transferred to the sugars. This step is called “reduction” because NADPH donates electrons to the 3-phosphoglyceric acid molecules to create glyceraldehyde-3 phosphate.

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