Thylakoid
The Thylakoid is a disk-shaped membrane structure inside the Chloroplast where the Light-Dependent Reactions occur. Its membrane contains Chlorophyll and accessory Pigments organized into Photosystem I and Photosystem II. The thylakoid lumen is the site of Photolysis, where water is split to release oxygen, electrons, and protons. The protons contribute to a Proton Gradient that drives ATP production through ATP Synthase.