Terminal Respiration

Question 1

Describe, in outline, the pathway of electron movement from reduced substrates to oxygen in the mitochondrion.

Answer 1

The path of electron flow is NADH → NADH dehydrogenase complex → ubiquinone → cytochrome b-c1 complex → cytochrome c → cytochrome oxidase complex → molecular oxygen (O2). The respiratory enzyme complexes couple the energetically favorable transport of electrons to the pumping of H+ out of the matrix.

Question 2

Describe, in outline, the generation of a proton concentration gradient across the inner mitochondrial membrane, and how this is used to convert ADP to ATP.

Answer 2

The ETC is a collection of proteins bound to the inner mitochondrial membrane and organic molecules, which electrons pass through in a series of redox reactions, and release energy. The energy released forms a proton gradient, which is used in chemiosmosis to make a large amount of ATP by the protein ATP-synthase.