If antibody binds to normal tissues it can cause damage to the body or create other disease symptoms. Rheumatoid arthritis is a good example of an autoimmune disease. Antibodies that react with body tissues are felt to contribute to joint swelling and pain.
In eukaryotic cells the pyruvate decarboxylation occurs inside the mitochondria, after transport of the substrate, pyruvate, from the cytosol. The transport of pyruvate into the mitochondria is via a transport protein and is active, consuming energy. Passive diffusion of pyruvate into the mitochondria is impossible because it is a polar molecule. On entry to the mitochondria the pyruvate decarboxylation occurs, producing acetyl CoA.
Pyruvate enters the Krebs cycle via an intermediate called acetyl CoA. Pyruvate is formed in the cytoplasm as the end product of glycolysis. Pyruvate enters a mitochondrion, in the matrix of which it encounters the enzyme pyruvate dehydrogenase. This enzyme catalyzes the reaction of pyruvate with coenzyme A to form acetyl CoA. This reaction is sometimes called the link reaction, as it links glycolysis to the Krebs cycle (= citric acid cycle, or tricarboxylic acid cycle).