Photophosphorylation - the thylakoid membrane Electrons are transfered through a series of thylakoid membrane proteins, resulting in a proton gradient. The inside of the membrane becomes acidic, and the protons return to the stroma by way of the ATP synthase. ATP synthase is a protein which builds ATP using potential energy stored in the proton gradient. The Light Reactions Broad daylight is cool Light Energy Light reactions are the energy transduction reactions.
Light reactions take place on the actual thylakoid membrane.
Light reactions contain photosystems I, II, or both. The two systems are compared in the following table. Photosystems I and II are both used in this process. Water is split into oxygen, protons, and electrons. The electrons from water are used for chlorophyll molecules that have donated electrons.