Question

Which of the following events takes place in the electron transport chain?A) the breakdown of glucose into two pyruvate moleculesB) the breakdown of an acetyl group to carbon dioxideC) the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycleD) substrate-level phosphorylation

Answer 1

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.