Question:
Citrate used in fatty acid synthesis uses which enzyme?
Citrate used in fatty acid synthesis uses which enzyme?
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Which cytosolic enzyme splits citrate back into acetyl-CoA for lipogenesis?
Updated On: Jun 24, 2026
- Citrate synthase
- ATP citrate lyase
- Aconitase
- Malic enzyme
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The Correct Option is B
Solution and Explanation
Step 1: Fatty acid synthesis occurs in the cytosol and needs acetyl-CoA as its building block. Acetyl-CoA is generated in the mitochondrial matrix but cannot cross the inner mitochondrial membrane directly.
Step 2: To export it, acetyl-CoA condenses with oxaloacetate inside the mitochondrion to form citrate (the first reaction of the citric acid cycle). Citrate then moves out to the cytosol through the tricarboxylate transporter in exchange with malate.
Step 3: In the cytosol, the enzyme ATP citrate lyase cleaves citrate back into acetyl-CoA and oxaloacetate, consuming ATP. The released cytosolic acetyl-CoA is then used for fatty acid synthesis.
Step 4: Why the others are wrong. Citrate synthase and aconitase act inside the mitochondrial citric acid cycle, and malic enzyme generates NADPH from malate. None of these cleaves citrate in the cytosol for lipogenesis.
Hence the answer is ATP citrate lyase.
Step 2: To export it, acetyl-CoA condenses with oxaloacetate inside the mitochondrion to form citrate (the first reaction of the citric acid cycle). Citrate then moves out to the cytosol through the tricarboxylate transporter in exchange with malate.
Step 3: In the cytosol, the enzyme ATP citrate lyase cleaves citrate back into acetyl-CoA and oxaloacetate, consuming ATP. The released cytosolic acetyl-CoA is then used for fatty acid synthesis.
Step 4: Why the others are wrong. Citrate synthase and aconitase act inside the mitochondrial citric acid cycle, and malic enzyme generates NADPH from malate. None of these cleaves citrate in the cytosol for lipogenesis.
Hence the answer is ATP citrate lyase.
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