Biochemistry Kerbs Cycle 937b097f Which step in TCA cycle is irreversible? A Succinate thiokinase B Alpha ketoglutarate dehydrogenase C ISO citrate dehydrogenase D Aconitase High-Yield Explanation Ans. (b) Alpha ketoglutarate dehydrogenaseRef: Harper's Biochemistry 28/e, ch-9, p 306