Which statement best describes the function of electron transport complexes?

The function of electron transport complexes is best described by the statement that they pass electrons along a series of reactions, ultimately leading to the formation of a proton gradient. In cellular respiration, specifically during oxidative phosphorylation, electron transport complexes are part of the inner mitochondrial membrane where they facilitate the transfer of electrons derived from the oxidation of NADH and FADH2. As electrons move through these complexes (I, II, III, and IV), they release energy, which is used to pump protons (H+ ions) from the mitochondrial matrix into the intermembrane space.

This movement of protons creates a proton gradient across the membrane, a form of potential energy known as the proton motive force. This gradient is crucial for ATP synthesis, as protons flow back into the mitochondrial matrix through ATP synthase, driving the production of ATP from ADP and inorganic phosphate. Therefore, this mechanism underpins the efficiency of energy production in cells, positioning the transport of electrons and the generation of the proton gradient as pivotal functions of the electron transport complexes.