Malonyl-CoA is a crucial molecule in cellular metabolism, primarily involved in the synthesis of fatty acids. It is formed from acetyl-CoA through the action of the enzyme acetyl-CoA carboxylase, which adds a carboxyl group to acetyl-CoA. This process requires energy in the form of ATP and biotin as a cofactor. In addition to its role in fatty acid synthesis, Malonyl-CoA also plays a regulatory role in metabolism. It inhibits carnitine palmitoyltransferase I, an enzyme involved in the transport of fatty acids into the mitochondria for oxidation. This regulation helps balance energy storage and expenditure in the body.