Photolysis is the breakdown of water into hydrogen and oxygen using the light during the photosynthesis process. It requires light energy and oxygen evolving complex (OEC) and an electron carrier. The oxygen-evolving complex is a water-oxidizing enzyme involved in the photo-oxidation of water during the light reactions of photosynthesis. Manganese and calcium are present in the core of the OEC, which is essential for photolysis of water.