The link reaction connects the anaerobic process of glycolysis, which occurs in the cytoplasm, to the aerobic steps of respiration, which occur in the mitochondria.

The link reaction occurs in the mitochondrial matrix in eukaryotic cells.

Pyruvate + NAD + coenzyme A (CoA) ➔ acetyl CoA + reduced NAD + carbon dioxide (CO₂)

In eukaryotic cells, pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins.

Pyruvate undergoes decarboxylation (removal of carbon dioxide) and oxidation (removal of two hydrogens) to form acetate.

Coenzyme A binds to acetate (two-carbon acetyl group), forming acetyl coenzyme A.

Acetyl coenzyme A delivers the acetyl group to the next stage of aerobic respiration, known as the Krebs cycle.

NAD is a coenzyme that accepts the hydrogens removed from pyruvate during the link reaction, forming reduced NAD.

The reduced NAD is used in oxidative phosphorylation to synthesise ATP.

The carbon dioxide will either diffuse away and be removed from the organism as a metabolic waste, or it may be used as a raw material in photosynthesis.