CARBOHYDRATE METABOLISM Utilized-Oxidized-Reduced-Acid

In the complete oxidation of fuel molecules relatively little ATP is produced directly by substrate-level phosphorylation (Section 12.5). Irrespective of the metabolic fuel (carbohydrates, fatty acids or amino acids), most of the ATP is derived from the electrons released on the reoxidation of coenzymes, NADH or FADHj. During dehydrogenase-catalysed reactions, electrons are removed from substrates and transferred to coenzymic acceptors which in turn deliver the electrons to an organization of numerous proteins, called an electron-transport assembly. These assemblies are located in the inner membrane of mitochondria, in chloroplast thylakoids (Section 9.5) or in the plasma membrane of bacteria. Electrons are passed along the assembly to molecular oxygen, the final acceptor, which is reduced in the presence of protons to water. During their transfer from component to component, a portion of their energy is released and may be conserved by utilization in the phos-... 

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