is the conversion of pyruvate to acetyl coa reversible
Upon entry to the mitochondria, the pyruvate is decarboxylated, producing acetyl CoA. This irreversible reaction traps the acetyl CoA within the mitochondria (the acetyl-CoA can only be transported out of the mitochondrial matrix under conditions of high oxaloacetate via the citrate shuttle, a TCA intermediate that is normally sparse). The carbon dioxide produced by this reaction is nonpolar and small, and can diffuse out of the mitochondria and out of the cell.
Pyruvate dehydrogenase complex