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Berg JM, Tymoczko JL, Stryer L. Biochemisattempt. fifth edition. New York: W H Freeman; 2002.


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Figure

Mitochondria, Stained Environment-friendly, Form a Netjob-related Inside a Fibroblast Cell(Left). Mitochondria oxidize carbon fuels to develop cellular power. Thistransformation calls for electron carry with several large proteincomplexes (above), some of which pump (more...)


The NADH and also FADH2 formed in glycolysis, fatty acid oxidation, and also thecitric acid cycle are energy-rich molecules bereason each contains a pair ofelectrons having a high transport potential. When these electrons are offered to reducemolecular oxygen to water, a big amount of complimentary energy is liberated, which can besupplied to generate ATP. Oxidative phosphorylation is the procedure in which ATPis formed as a result of the deliver of electrons from NADH or FADH2to O2by a collection of electron carriers. This procedure, which takes placein mitochondria, is the significant source of ATP in aerobic organisms (Figure 18.1). For example, oxidativephosphorylation generates 26 of the 30 molecules of ATP that are created when glucoseis completely oxidized to CO2 and H2O.


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Oxidative phosphorylation is conceptually simple and also mechanistically facility. Without a doubt,the unraveling of the system of oxidative phosphorylation has actually been among thethe majority of challenging troubles of biochemisattempt. The circulation of electrons from NADH orFADH2 to O2 with protein complexes situated in themitochondrial inner membrane leads to the pumping of proloads out of themitochondrial matrix. The resulting uneven circulation of protons geneprices a pHgradient and also a transmembrane electrical potential that creates aproton-motive force. ATP is synthesized as soon as protons flow backto the mitochondrial matrix with an enzyme complicated. Therefore, the oxidationof fuels and the phosphorylation of ADP are coupled by a proton gradient acrossthe inner mitochondrial membrane (Figure 18.2).


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Figure 18.2

Essence of Oxidative Phosphorylation. Oxidation and also ATP synthesis are coupled by transmembrane protonfluxes.


Oxidative phosphorylation is the culmicountry of a collection of energychanges that are referred to as cellular respirationor ssuggest respiration in their totality. First, carbon fuels areoxidized in the citric acid cycle to yield electrons with high move potential.Then, this electron-motive force is converted right into a proton-motive force and also,lastly, the proton-motive pressure is converted into phosphoryl deliver potential.The convariation of electron-motive force into proton-motive force is lugged out by3 electron-pushed proton pumps—NADH-Q oxidoreductase, Q-cytochromec oxidoreductase, and also cytochrome c oxidase.These huge transmembrane complexes contain multiple oxidation-reduction centers,including quinones, flavins, iron-sulfur clusters, hemes, and copper ions. The finalphase of oxidative phosphorylation is lugged out by ATP synthase,an ATP-manufacturing assembly that is thrust by the circulation of proloads back right into themitochondrial matrix. Contents of this impressive enzyme turn as component of itscatalytic mechanism. Oxidative phosphorylation vividly reflects that protongradients are an interconvertible currency of free energy in biologicalunits.

Respiration—

An ATP-generating process in which an inorganic compound (such as molecularoxygen) serves as the ultimate electron acceptor. The electron donor can beeither an organic compound or an not natural one.

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18.1. Oxidative Phosphorylation in Eukaryotes Takes Place in Mitochondria18.2. Oxidative Phosphorylation Depends on Electron Transfer18.3. The Respiratory Chain Consists of Four Complexes: Three Proton Pumps and also a Physical Link to the Citric Acid Cycle18.4. A Proton Gradient Powers the Synthesis of ATP18.5. Many kind of Shuttles Allow Movement Across the Mitochondrial Membranes18.6. The Regulation of Cellular Respiration Is Governed Primarily by the Need for ATPSummaryProblemsSchosen Readings

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