Final answer:
The rate limiting step for fatty acid synthesis is the formation of malonyl-CoA from acetyl-CoA, catalyzed by the enzyme acetyl-CoA carboxylase.
Step-by-step explanation:
The rate limiting step for fatty acid synthesis is the formation of malonyl-CoA from acetyl-CoA. This step is catalyzed by the enzyme acetyl-CoA carboxylase, which is regulated by both allosteric control and covalent modification. Acetyl-CoA carboxylase is the only regulated enzyme in fatty acid synthesis and its activity determines the overall rate of fatty acid synthesis.