Photosystem I

Photosystem I

Photosystem I (PSI) is a protein-pigment complex found in the Thylakoid membrane that absorbs light energy, primarily at 700 nm wavelengths. It plays a crucial role in the second stage of the Light-Dependent Reactions. Electrons from Photosystem II are re-energized here and transferred to the protein ferredoxin. These electrons are ultimately used to reduce NADP++ into NADPH, which is necessary for the Calvin Cycle.