In photosynthesis, light energy is absorbed by chlorophyll molecules in the photosystems. This energy is used to excite electrons from these chlorophyll molecules, which are then transferred to primary electron acceptors. These primary electron acceptors are usually quinones, which are reduced to quinols. The reduced quinols can then donate electrons to the electron transport chain, which is a series of membrane-bound proteins that use the energy of the electron flow to pump protons across the membrane. This creates a proton gradient that is used to generate ATP, the energy currency of the cell.
