Fatty acid synthesis occurs in the cytosol of hepatocytes. The committed, rate-limiting step is catalyzed by acetyl-CoA carboxylase (ACC). Which molecule is the direct product of the ACC reaction?
- A Acetoacetyl-CoA
- B Propionyl-CoA
- C Malonyl-CoA ✓
- D Succinyl-CoA
Correct answer: C. Malonyl-CoA
Explanation
Acetyl-CoA carboxylase uses biotin as a cofactor and CO2 as the carboxyl donor in an ATP-dependent reaction to convert acetyl-CoA to malonyl-CoA. Malonyl-CoA is the 2-carbon donor for each elongation cycle catalyzed by fatty acid synthase. Notably, malonyl-CoA simultaneously inhibits carnitine palmitoyltransferase-I (CPT-I), preventing futile co-activation of fatty acid oxidation during active synthesis.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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