Chemiosmotic theory readily explains the dependence of electron transfer on ATP synthesis in mitochondria.Because oligomycin is known to interact not directly with the electron carriers but with ATP synthase, it follows that electron transfer and ATP synthesis are obligately coupled neither reaction occurs without the other.More surprising is the finding that the converse is also true: inhibition of ATP synthesis blocks electron transfer in intact mitochondria.Because the energy of substrate oxidation drives ATP synthesis in mitochondria, we would expect inhibitors of the passage of electrons to O2 to block ATP synthesis.When isolated mitochondria are suspended in a buffer containing ADP, Pi, and an oxidizable substrate such as succinate, three easily measured processes occur: (1) the substrate is oxidized (succinate yields fumarate), (2) O2 is consumed, and (3) ATP is synthesized.Mitchell used “chemiosmotic” to describe enzymatic reactions that involve, simultaneously, a chemical reaction and a transport process.To emphasize this crucial role of the proton motive force, the equation for ATP synthesis is sometimes written asĪDP + Pi + nH P + -> ATP + H 2 O + nH N+.According to the model the electrochemical energy inherent in the difference in proton concentration and separation of charge across the inner mitochondrial membrane-the proton-motive force-drives the synthesis of ATP as protons flow passively back into the matrix through a proton pore associated with ATP synthase. ![]() The chemiosmotic model was proposed by Peter Mitchell.But what is the chemical mechanism that couples proton flux with phosphorylation?.The proton-motive force conserves, more than enough free energy (about 200 kJ) per “mole” of electron pairs to drive the formation of a mole of ATP, which requires about 50 kJ.Oxidative phosphorylation by Chemiosmotic coupling hypothesis
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