Coenzyme A (CoA) is a vital cofactor in cellular metabolism, serving as a carrier for acyl groups in numerous enzymatic reactions. It plays a central role in the citric acid cycle, fatty acid oxidation and synthesis, and the metabolism of carbohydrates, amino acids, and ketone bodies. Structurally, it consists of adenosine 3',5'-diphosphate linked to pantothenic acid and cysteamine via a pyrophosphate bridge. The terminal thiol group forms thioester bonds with acyl groups, activating them for transfer. CoA is synthesized from pantothenic acid (vitamin B5), cysteine, and ATP. It is highly polar and functions primarily in aqueous cellular environments. Deficiency is rare but can impair energy metabolism.