7.3—Link reaction and Krebs cycle

In the mitochondrial matrix, pyruvate is decarboxylated and dehydrogenated, forming acetyl CoA, carbon dioxide and reduced NAD. Acetyl CoA then joins oxaloacetate; the Krebs cycle releases CO₂, reduces NAD/FAD and makes ATP while regenerating oxaloacetate.

Each glucose produces two pyruvate, so the link reaction and cycle turn twice per glucose. The cycle is sustained because the acceptor molecule is regenerated.

One glucose gives two acetyl CoA, two CO₂ and two reduced NAD in the link reaction; two turns of the cycle then yield four CO₂, six reduced NAD, two reduced FAD and two ATP.

No ATP is made directly in the link reaction. The Krebs cycle is not “in the mitochondrion” generally; its matrix location and carbon accounting matter.