Calculate the energy yield of glycolysis and cellular respiration per glucose molecule. Distinguish between substrate-level phosphorylation and oxidative phosphorylation. Where does the energy for oxidative phosphorylation come from?

A total of 32 ATP molecules per glucose molecule is generated in cellular respiration and glycolysis. In substrate-level phosphorylation, ATP is generated from the coupled reactions whereas in oxidative phosphorylation ATP is formed by using the oxidized NADH and FADH cofactors. The energy for oxidative phosphorylation comes from the movement of proton to the matrix of mitochondria through ATP synthase.

Explanation:

Each molecule of glucose utilizes 2 ATP molecules and breaks down into 2 pyruvate molecules and generates 4 ATP from substrate-level phosphorylation and 2 molecules of NADH.

Pyruvate converts into acetyl Co-A and produces 2 molecules of NADH. In citric acid cycle, the 2 molecules of acetyl Co-A produces 2 molecules of GTP/ATP, 6 molecules of NADH, 2 molecules of FADH2.

In oxidative phosphorylation 1 molecule of NADH contributes to the production of 2.5ATP, FADH2 gives 1.5ATP. Hence the total production of ATP is 4 + 2 + 25 + 3 = 34 - 2 ATP (used early in glycolysis) = 32 ATP (net ATP production).