Fatty acid synthesis requires cytosolic acetyl-CoA, but pyruvate-derived acetyl-CoA is generated inside mitochondria. Which enzyme releases this acetyl-CoA into the cytosol?
- A Citrate synthase
- B ATP-citrate lyase ✓
- C Malate dehydrogenase
- D Pyruvate carboxylase
Correct answer: B. ATP-citrate lyase
Explanation
In the fed state, mitochondrial acetyl-CoA condenses with oxaloacetate to form citrate, which crosses the inner mitochondrial membrane via the tricarboxylate transporter. In the cytosol, ATP-citrate lyase cleaves citrate back into acetyl-CoA and oxaloacetate. Citrate synthase works only inside mitochondria in the opposite direction, and malate dehydrogenase regenerates oxaloacetate within the shuttle without releasing acetyl-CoA. Pyruvate carboxylase supplies mitochondrial oxaloacetate.
Reference: Lehninger Principles of Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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