Answer :
Final answer:
The reduction stage of the Calvin cycle occurs during the reduction of PGA to G3P. ATP and NADPH are used in this stage to convert PGA into G3P, which is an important step in the production of carbohydrate molecules.
Explanation:
The reduction stage of the Calvin cycle occurs during the reduction of PGA to G3P. In this stage, ATP and NADPH are used to convert PGA (3-phosphoglycerate) into G3P (glyceraldehyde 3-phosphate) through a reduction reaction, which involves the gain of electrons. This process is essential for the production of carbohydrate molecules from G3P, which can ultimately be used to generate glucose.