Question

In which parts of the Calvin cycle are high-energy phosphate groups donated by ATP to boost the energy of reactions?

a) In the regeneration phase
b) During the carbon fixation phase
c) In the reduction phase
d) Throughout the cycle

Answer 1

ATP is used in two phases of the Calvin cycle; mainly in the reduction phase, with large amounts of ATP and NADPH reducing 3-phosphoglycerate into GA3P, and in the regeneration phase, where ATP is used to regenerate RuBP.

Step-by-step explanation:

High-energy phosphate groups donated by ATP to boost the energy of reactions in the Calvin cycle are primarily used during the reduction phase and the regeneration phase. In the reduction phase, ATP and NADPH are used to reduce 3-phosphoglycerate into Glyceraldehyde-3-phosphate (GA3P). It is during this phase that a total of 12 ATP and 12 NADPH molecules are used over six turns of the cycle. Furthermore, in the regeneration phase of the cycle, 6 ATP molecules are utilized to regenerate ribulose bisphosphate (RuBP) from GA3P, which is necessary for the cycle to continue. This detailed breakdown shows that while ATP is used during two distinct phases, the majority of ATP is used in the reduction of 3-phosphoglycerate to GA3P.