Final answer:
NADPH is most directly formed from Photosystem I during the light-dependent reactions, which provide energy for the Calvin cycle's glucose production.
Step-by-step explanation:
NADPH forms most directly from Photosystem I during the light-dependent reactions of photosynthesis. In Photosystem I, after light photons are absorbed, excited electrons are transferred to a series of proteins and small molecules embedded in the thylakoid membrane. Eventually, these electrons are used to reduce NADP+ to NADPH, a critical energy-carrying molecule that, along with ATP, will be utilized in the light-independent reactions, such as the Calvin cycle, to fix carbon and produce glucose. Notably, ATP synthase is involved in synthesizing ATP, another important product of the light-dependent reactions, by utilizing the proton gradient established by the activity of the cytochrome b6f complex and the flow of electrons through the electron transport chain.
NADPH forms most directly from Photosystem I in the light-dependent reactions of photosynthesis. In Photosystem I, light energy is used to excite electrons, which are then transferred to a primary electron acceptor. These electrons are ultimately used to reduce NADP+ to NADPH.