The products of light reactions ATP and NADPH are used in which of the following phases of Calvin cycle.

The products of light reactions, ATP and NADPH, are used in the reduction phase of the Calvin cycle.

Here's a step-by-step breakdown:

1. The Calvin cycle begins with the carbon fixation phase, where CO2 is incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP). This process is catalyzed by the enzyme RuBisCO.

2. The product of this reaction is an unstable six-carbon compound that immediately splits into two molecules of a three-carbon compound, 3-phosphoglycerate (3-PGA).

3. In the next phase, the reduction phase, ATP and NADPH produced in the light reactions are used. Each molecule of 3-PGA receives an additional phosphate group from ATP, becoming 1,3-bisphosphoglycerate.

4. Subsequently, a pair of electrons donated from NADPH reduces 1,3-bisphosphoglycerate, which loses a phosphate group in the process, to become glyceraldehyde 3-phosphate (G3P).

5. Some of the G3P molecules are used to make glucose and other organic molecules.

6. The remaining G3P molecules are used in the regeneration phase of the Calvin cycle to regenerate RuBP, which enables the cycle to continue.

So, the ATP and NADPH produced in the light reactions are crucial for the reduction phase of the Calvin cycle.