Question

Which of the following are part of the chemiosmotic coupling model? Protons are pumped out of the mitochondrial matrix into the intermembrane space. The active transport of protons is driven by the free energy derived from electron transport. Increasing the concentration of protons in the intermembrane space creates an electrical potential and a pH imbalance that releases energy upon proton flow back into the matrix. The energy released by the return of protons to the matrix is what drives ATP synthesis.

Answer 1

The correct answer is: Protons are pumped out of the mitochondrial matrix into the intermembrane space

Chemiosmosis can be described as movement of ions across a selectively permeable membrane, down their electrochemical gradient. It occurs during the cellular respiration within mitochondria and it is involved in ATP synthesis (oxidative phosphorylation via ATP synthase).

Electrons from electron carriers (NADH and FADH) 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.