BOTANY

BOTANY

CYTOLOGY

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What is the second stage of the Calvin Cycle called?
A
carbon dioxide fixation
B
carbon dioxide reduction
C
carbon dioxide RuBP
D
regeneration of RuBP
Explanation: 

Detailed explanation-1: -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-2: -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-3: -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. In summary, it takes six turns of the Calvin cycle to fix six carbon atoms from CO2.

Detailed explanation-4: -Atmospheric carbon dioxide is converted to glucose during the Calvin-Benson cycle. This requires the overall reduction of CO2, using the electrons available from the oxidation of NADPH. Thus the dark reactions represent a redox pathway. NADPH is oxidized to NADP+ and CO2 is reduced to glucose.

Detailed explanation-5: -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. In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue.

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