This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
ratelimiting enzyme in fatty acid synthesis ? 
Select and explain. 
A. malonyl co a synthase, B. acyl co synthase, C. malonyl co a reductase, D. cholestrol acyl transferase
A: malonyl co a synthase
Answer: A: malonyl co a synthase 
Explanation: Fatty Acid Synthesis * Fatty acids are built from 2-C units derived from acetyl-CoA * Acetate units are activated for transfer to growing FA chain by conversion to malonyl-CoA * Decarboxylation of malonyl-CoA and reducing power of NADPH drive chain growth * Chain grows to 16-carbons (eight acetyl-CoAs) * Other enzymes add double bonds and more ref : lipincott 9th ed