Here's how it works:
* Light-dependent reactions: In the thylakoid membranes of chloroplasts, light energy is captured by chlorophyll and used to split water molecules. This process generates electrons, protons (H+), and oxygen.
* Electron transport chain: These electrons are passed down an electron transport chain, releasing energy that is used to pump protons across the thylakoid membrane. This creates a proton gradient, which is then used to generate ATP (adenosine triphosphate), the primary energy currency of cells.
* NADPH production: At the end of the electron transport chain, the electrons are used to reduce NADP+ to NADPH.
* Calvin cycle: NADPH carries the electrons to the Calvin cycle, where they are used to reduce carbon dioxide (CO2) into glucose, a sugar molecule.
So, NADPH acts as a reducing agent, carrying high-energy electrons from the light-dependent reactions to the Calvin cycle, where they are essential for making sugar.
