NADPH (reduced NADP⁺) is produced in Photosystem I (PSI) during the light-dependent reactions of photosynthesis. In PSI, light energy boosts electrons to a very high energy level; these electrons are captured by ferredoxin and then used by ferredoxin-NADP⁺ reductase (FNR) to reduce NADP⁺ to NADPH. NADPH is then used in the Calvin cycle (light-independent reactions) to reduce 3-phosphoglycerate (3-PGA) to glyceraldehyde-3-phosphate (G3P).