Aresearcher follows a protocol to test the activity of a mitochondrial extract containing all of the soluble enzymes of the matrix. because the mitochondrial extract was dialyzed, the protocol lists low molecular weight cofactors that must be added to the extract in order to catalyze the oxidation of acetyl-coa to co2. the list does not include lipoic acid, a known cofactor of the citric acid cycle. why is lipoic acid omitted from the list of cofactors to add back to the extract?