In the non-cyclic photophosphorylation of the light dependent stage, NADP acts as a hydrogen carrier. NADP reductase catalyses the reduction of NADP to NADPH. NADP is the final electron acceptor. The NADPH produced is used in the light independent reaction; a pair of electrons donated from NADPH reduces 1.3-bisphosphoglycerate to triose phosphate (TP). For every three molecules of co2 entering the Calvin cycle, 3 molecules of RuBP are carboxylated and 6 molecules of TP are formed; 1 molecule of TP is the net gain, while the other 5 are recycled to regenerate RuBP for carbon dioxide fixation. The TP formed at the end of the Calvin cycle becomes the starting material for metabolic pathways that synthesize other organic compounds including carbohydrates, lipids, proteins, nucleic acids and chlorophyll.
