Question: is the conversion of pyruvate to acetyl coa reversible

Answer: No, 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.