The correct answer is: C) the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle
Electrons from electron carriers (NADH and FADH from glycolysis and citric acid cycle) donate electrons to the electron transport chain and that causes changes in protein complexes of electron transport chain. As a consequence, protein complexes pump H+ across a selectively permeable cell membrane from the mitochondrial matrix into the intermembrane space of mitochondria. H+ can only get back and pass through the inner mitochondrial membrane with the help of ATP synthase (down their electrochemical gradient). ATP synthase turned by the force of the H+ diffusing through it forms ATP by adding a phosphate to ADP. This type of ATP synthesis is called oxidative phosphorylation and it is based on chemiosmosis-movement of ions across a selectively permeable membrane.
