Answer :
The Calvin cycle, also known as the light-independent reactions or the dark reactions, is an essential part of photosynthesis that takes place in the chloroplasts of plant cells. It does not require light and is primarily responsible for synthesizing glucose from carbon dioxide using the energy molecules produced in the light-dependent reactions.
Here's a breakdown of the choices to determine which one does not occur during the Calvin cycle:
ATP is regenerated through the phosphorylation of ADP: In the Calvin cycle, ATP is consumed rather than regenerated. It provides energy for the conversion of molecules, but its regeneration occurs during the light-dependent reactions, not the Calvin cycle itself.
3-phosphoglyceric acid (3-PGA) is converted into glyceraldehyde 3-phosphate (G3P): This step occurs during the Calvin cycle. ATP and NADPH (produced in the light-dependent reactions) are used to convert 3-PGA into G3P.
RuBP is regenerated: Ribulose bisphosphate (RuBP) is regenerated during the Calvin cycle to allow the cycle to continue. This is an essential part of the cycle, ensuring that carbon fixation can proceed in the next turn.
RuBisCO catalyzes a reaction between carbon dioxide and RuBP: RuBisCO is a crucial enzyme in the Calvin cycle that catalyzes the first step, which is the fixation of carbon dioxide to RuBP.
From this analysis, the correct answer is:
- ATP is regenerated through the phosphorylation of ADP
This does not happen in the Calvin cycle as ATP is consumed rather than regenerated during this process.