Photosynthesis: What Powers the Splitting of Water?

Question

The splitting of water is an endergonic (non-spontaneous) reaction, and thus would require energy (chemical work to be done) in order to happen. In Photosystem II, an enzyme catalyzes this splitting, but where does it get the energy from? Does it use ATP?

Answer 1

Photosysten II contains an enzyme made of the D1 and D2 subunits. Within that enzyme, there is another structure that is known as the Oxygen Evolving Complex. Oxidation of water in Photosynthesis occurs at the OEC with the help of a manganese cofactor that remains bound to the OEC. The process of oxidizing water with the OEC involves photo-oxidation, with photons of light being absorbed by other parts of the D1 and D2 subunits that participate in the overall oxidation reaction. The enzyme does a bit of catalytic magic here that isn't well understood, but ATP is not required at this step.

The best model to reference is cited here:

Dolai, U (2017). "Chemical Scheme of Water -Splitting Process during Photosynthesis by the way of Experimental Analysis". IOSR Journal of Pharmacy and Biological Sciences. 12 (6): 65–67.