process

Oxidative phosphorylation

Oxidative phosphorylation is the process by which ATP synthesis is coupled to the movement of electrons through the mitochondrial electron transport chain and the associated consumption of oxygen.2,3,6 This process is the most efficient for ATP synthesis, generating approximately 36 ATP molecules per glucose molecule, compared to the two molecules of ATP generated during glycolysis.2,3,6 The free energy released by stepwise oxidation reactions between NADH, FADH2, and ubiquinol pumps protons from the mitochondrial matrix, across the mitochondrial inner membrane, and into the intermembrane space.2,3,6 This pumping action creates a tremendous proton concentration imbalance between the intermembrane space and the matrix.2,3,6 The potential energy stored in this proton gradient is then used to power ATP synthase phosphorylating ADP to generate ATP.2,3,6 The electron transport chain (Fig. 5.3) involves the transfer of electrons from NADH and FADH2 to ubiquinone (also called Coenzyme Q) through a series of four large protein complexes that reside in the mitochondrial inner membrane.2,3,6 Because the electrons begin the process at a high energy state and end the process in a low energy state, the electron transport chain entails the stepwise release of energy, which the protein complexes harness in order to pump protons from the mitochondrial matrix into the intermembrane space; each reaction in the electron transport chain represents a slight decrease in the energy of the electrons as they pass from complex to complex.2,3,6 An oxygen molecule sits at the end of the electron transport chain as the final electron acceptor, where it joins with two free protons to become water in a highly exothermic reaction.2,3,6 Without oxygen, the electrons in the electron transport chain cannot continue to fall down their potential energy gradient, and progression of electrons through the transport chain stops.2,3,6

Ref:
BOOK CHAPTER Metabolism in Surgical Patients Elizabeth E. Blears, Joshua S. Carson, Celeste C. Finnerty, Evan Ross, Christian Sommerhalder and David N. Herndon Sabiston Textbook of Surgery, Chapter 5, 95-118.e1

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Added on Oct 2, 2022 by Barbara Van De Keer

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