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Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants , algae , and cyanobacteria .
Photosystem II obtains electrons by oxidizing water in a process called photolysis. Molecular oxygen is a byproduct of this process, and it is this reaction that supplies the atmosphere with oxygen. The fact that the oxygen from green plants originated from water was first deduced by the Canadian-born American biochemist Martin David Kamen.
The electrons from the initial light reaction reach Photosystem I, then are raised to a higher energy level by light energy and then received by an electron acceptor and reduce NADP + to NADPH. The electrons lost from Photosystem II get replaced by the oxidation of water, which is "split" into protons and oxygen by the oxygen-evolving complex ...
It is an enzyme that accepts electrons from electron-transferring flavoprotein in the mitochondrial matrix, and uses these electrons to reduce ubiquinone. [30] This enzyme contains a flavin and a [4Fe–4S] cluster, but, unlike the other respiratory complexes, it attaches to the surface of the membrane and does not cross the lipid bilayer.
The cathode is the electrode where reduction (gain of electrons) takes place (metal B electrode); in a galvanic cell, it is the positive electrode, as ions get reduced by taking up electrons from the electrode and plate out (while in electrolysis, the cathode is the negative terminal and attracts positive ions from the solution).
Commercially, electrolytic cells are used in the electrorefining and electrowinning of several non-ferrous metals. Most high-purity aluminum, copper, zinc, and lead are produced industrially in electrolytic cells. As already noted, water, particularly when ions are added (saltwater or acidic water), can be electrolyzed (subjected to electrolysis).
An electrochemical gradient is analogous to the water pressure across a hydroelectric dam. Routes unblocked by the membrane (e.g. membrane transport protein or electrodes ) correspond to turbines that convert the water's potential energy to other forms of physical or chemical energy, and the ions that pass through the membrane correspond to ...
First, cells may transfer electrons directly to each other without the need for an intermediary substance. Pelotomaculum thermopropioncum has been observed linked to Methanothermobacter thermautotrophicus by a pilus (external cell structures used in conjugation and adhesion ) that was determined to be electrically conductive.