Pyruvate formed during glycolysis enters mitochondrial matrix and undergoes oxidative decarboxylation by a complex set of reactions catalysed by pyruvic dehydrogenase and NADH, acetyl CoA and CO2 is produced.
Pyruvic +CoA+NAD+Mg2+Pyruvate dehydrogenase
Acetyl CoA+CO2+NADH+H+
Acetyl CoA enters the TCA cycle.