fatty acids are bound to a molecule called ACP (acyl carrier protein) instead of CoA.
fatty acid biosynthesis begins with the formation of a three carbon molecule called malony-CoA. this comes about by the addition of a carboxyl group (biotin is a required coenzyme). the enzyme responsible for this reaction is acetyl CoA carboxylase. it is the only regulated enzyme in fatty acid biosynthesis and is activated by citrate and inhibited by palmitate. malonyl-CoA is readily converted to malonyl-ACP