Final answer:
The conversion of 3-phosphoglycerate (PGA) to glyceraldehyde-3-phosphate (G3P) in the Calvin cycle is facilitated by phosphoglycerate kinase and glyceraldehyde-3-phosphate dehydrogenase, utilizing ATP and NADPH from the light-dependent reactions.
Step-by-step explanation:
The enzyme responsible for the conversion of 3-phosphoglycerate (PGA) to glyceraldehyde-3-phosphate (G3P) in the Calvin cycle is phosphoglycerate kinase followed by glyceraldehyde-3-phosphate dehydrogenase. Initially, PGA is phosphorylated to 1,3-bisphosphoglycerate by phosphoglycerate kinase, using ATP. Subsequently, glyceraldehyde-3-phosphate dehydrogenase catalyzes the reduction of 1,3-bisphosphoglycerate to G3P, using NADPH as an electron donor. This two-step reaction involves the utilization of energy stored in ATP and NADPH, which are produced during the light-dependent reactions of photosynthesis. G3P is then used to regenerate ribulose bisphosphate (RuBP) and produce glucose.