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Ferredoxin: NADP + reductase is the last enzyme in the transfer of electrons during photosynthesis from photosystem I to NADPH. [2] The NADPH is then used as a reducing equivalent in the reactions of the Calvin cycle. [2] Electron cycling from ferredoxin to NADPH only occurs in the light in part because FNR activity is inhibited in the dark. [11]
In cellular metabolism, NAD is involved in redox reactions, carrying electrons from one reaction to another, so it is found in two forms: NAD + is an oxidizing agent, accepting electrons from other molecules and becoming reduced; with H +, this reaction forms NADH, which can be used as a reducing agent to donate electrons.
The NAD+/NADH coenzyme couple act as an electron reservoir for metabolic redox reactions, carrying electrons from one reaction to another. [5] Most of these metabolism reactions occur in the mitochondria. To regenerate NAD+ for further use, NADH pools in the cytosol must be reoxidized.
The electrons reach the P700 reaction center of photosystem I where they are energized again by light. They are passed down another electron transport chain and finally combine with the coenzyme NADP + and protons outside the thylakoids to form NADPH. Thus, the net oxidation reaction of water photolysis can be written as:
Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I [1] is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ferredoxin.
In enzymology, a hydrogen dehydrogenase (NADP+) (EC 1.12.1.3) is an enzyme that catalyzes the chemical reaction. H 2 + NADP + H + + NADPH. Thus, the two substrates of this enzyme are H 2 and NADP +, whereas its two products are H + and NADPH.
The electrons are then transferred through the FMN via a series of iron-sulfur (Fe-S) clusters, [10] and finally to coenzyme Q10 (ubiquinone). This electron flow changes the redox state of the protein, inducing conformational changes of the protein which alters the p K values of ionizable side chain, and causes four hydrogen ions to be pumped ...
This process occurs naturally in plants photosystem II to provide protons and electrons for the photosynthesis process and release oxygen to the atmosphere, [1] as well as in some electrowinning processes. [2] Since hydrogen can be used as an alternative clean burning fuel, there has been a need to split water efficiently.