Here's a breakdown:
* ATP: The light-dependent reactions use light energy to create a proton gradient across the thylakoid membrane. This gradient is then used by ATP synthase to produce ATP from ADP and inorganic phosphate (Pi).
* NADPH: Light energy is also used to excite electrons in chlorophyll, which then travel through an electron transport chain. These electrons are used to reduce NADP+ to NADPH.
Therefore, the light-dependent reactions act as a "power source" for the Calvin cycle. The ATP and NADPH generated in these reactions provide the energy and reducing power necessary for the Calvin cycle to synthesize glucose from carbon dioxide.
