Acetyl-CoA generated in the mitochondrial matrix cannot cross the inner membrane directly. Which enzyme converts cytosolic citrate back to acetyl-CoA so that it can serve as substrate for fatty acid synthesis?
- A Citrate synthase
- B ATP citrate lyase ✓
- C Aconitase
- D Isocitrate dehydrogenase
Correct answer: B. ATP citrate lyase
Explanation
The citrate shuttle transfers acetyl units from mitochondria to cytosol as citrate. In the cytosol, ATP citrate lyase cleaves citrate into acetyl-CoA and oxaloacetate using ATP, providing the acetyl-CoA that feeds acetyl-CoA carboxylase and fatty acid synthase. Citrate synthase works in the opposite direction inside mitochondria, forming citrate from acetyl-CoA and oxaloacetate, which kills option A.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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