During Calvin cycle, how does the energy carrier like the ATP utilized in the process?

The Calvin cycle, also known as the light-independent reactions or the dark phase of photosynthesis, utilizes ATP (adenosine triphosphate) as an energy source. Here's how it works:

1. Carbon Fixation: The Calvin cycle begins when a CO2 molecule combines with a five-carbon sugar called ribulose bisphosphate (RuBP) in a process known as carbon fixation. This reaction is catalyzed by the enzyme RuBisCO.

2. Reduction: The six-carbon compound formed in the first step immediately splits into two molecules of a three-carbon compound, 3-phosphoglycerate (3-PGA). ATP provides the energy for this reaction, converting into ADP (adenosine diphosphate) and a phosphate group.

3. Sugar Creation: The 3-PGA molecules are then converted into glyceraldehyde 3-phosphate (G3P) molecules, a three-carbon sugar. This step requires both ATP (which is converted back into ADP) and NADPH (which is converted into NADP+).

4. Regeneration of RuBP: Some of the G3P molecules are used to regenerate RuBP so that the cycle can continue. This step also requires ATP.

In summary, ATP is used in the Calvin cycle to provide the energy needed for the conversion of 3-PGA into G3P and the regeneration of RuBP. The ATP is converted back into ADP and a phosphate group, which can then be recharged during the light-dependent reactions of photosynthesis to form ATP again.