What actually splits the water in the light-dependent reaction in photosynthesis

Photosynthesis begins when a photon strikes photosystem II and excites an electron of chlorophyll P680. The excited electron is captured by the primary electron acceptor, pheophytin, and through a series of redox reactions, transferred to plastoquinone, PQ. A Z protein, associated with photosystem II, splits water into oxygen, hydrogen ions (protons), and electrons. One of these electrons are used to replace the missing electron in chlorophyll P680. Oxygen leaves the cell and the protons remain in the thylakoid space. The electron passes through a proton pump called the “Q cycle” involving various components of photosystem II, plastiquinone, and components of the b6–f cytochrome complex. The components of the Q cycle transport protons from the stroma into the thylakoid lumen, thus creating an H gradient for chemiosmosis. Then the electron passes through other components of an electron transport chain similar to that in cellular respiration, eventually replacing an electron that is lost by photosystem I when it is struck by a photon. The electron from photosystem I is passed to ferredoxin, then to the enzyme NADP reductase, which uses the electron and H ions from the stroma to reduce NADP to NADPH. Protons that accumulate in the thylakoid lumen form an electrochemical gradient that drives the phosphorylation of ADP to ATP as protons move through the ATPase complex from the thylakoid lumen into the stroma. Note that two electrons are required to reduce NADP to NADPH; thus, the entire process happens twice for each NADP reduced to NADPH.

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Great reply!

Thank you very much.  I understand the basics of photosynthesis but I couldn't find the information about the protein....that clears it up.

Thanks a bunch!!!!

Please mark as solved when you get a chance.