The electron transport chain results in the generation of:

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11ecba2d_0f24_3b55_a3bf_0bf2f57de3f9_MD0008_00 Oxidative phosphorylation is the final step in cellular respiration and takes place within the mitochondria. It is driven by energy from NADH and FADH₂, which are produced during glycolysis and the Citric acid cycle. These molecules enter the electron transport chain, where they initiate transfer of electrons through a series of energetically favorable redox reactions that end with O₂ as the final electron acceptor. These coupled redox reactions occur in transmembrane complexes that reside between the mitochondrial matrix and the intermembrane space. Because these reactions are energetically favorable, the excess energy can pump protons (H⁺) from the mitochondrial matrix to the intermembrane space. This establishes both a concentration and a charge gradient (collectively called an electrochemical gradient) across the membrane. The gradient drives the movement of protons from the intermembrane space (higher concentration) back into the matrix (lower concentration) through the ATP synthase complex. This energetically favorable movement of H⁺ down its electrochemical gradient (chemiosmosis) provides ATP synthase with the energy needed to phosphorylate ADP, forming ATP. (Choice B) Oxidative phosphorylation involves the oxidation of NADH, not the reduction of NAD⁺. In addition, redox reactions are driven by the transfer of electrons, not protons. (Choices C and D) The electron transport chain does not generate electrons but transfers electrons from one chemical species to another in successive coupling reactions. This process generates protons, which are pumped out of the mitochondrial matrix to establish an electrochemical gradient. Educational objective: In oxidative phosphorylation, a series of energetically favored redox reactions produces protons. The protons are pumped from the mitochondrial matrix to the intermembrane space, creating an electrochemical gradient that drives ATP synthesis.

The Electron Transport Chain Results in the Generation Of