Photosystem II
Photosystem II (PSII) is the first protein-pigment complex in the Light-Dependent Reactions, absorbing light energy most efficiently at 680 nm.
It initiates the process by exciting electrons, which are transferred down the Electron Transport Chain. Photolysis of water occurs at PSII to replenish lost electrons, producing oxygen and protons in the Thylakoid Lumen.
PSII is essential for creating the Proton Gradient used to generate ATP through ATP Synthase.