Question:medium
Citrate used in fatty acid synthesis uses which enzyme?
Citrate used in fatty acid synthesis uses which enzyme?
Show Hint
Which cytosolic enzyme splits citrate back into acetyl-CoA for lipogenesis?
Updated On: Jun 24, 2026
- Citrate synthase
- ATP citrate lyase
- Aconitase
- Malic enzyme
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Identify the transport problem. The carbon for new fatty acids is acetyl-CoA, made in the mitochondria, but lipogenesis happens in the cytosol and the mitochondrial inner membrane blocks acetyl-CoA from leaving directly.
Step 2: The cell solves this with the citrate shuttle. Acetyl-CoA is first packaged as citrate by joining oxaloacetate, carried out to the cytosol, and there it must be unpacked again to release the acetyl-CoA.
Step 3: The unpacking step in the cytosol is performed by ATP citrate lyase, which splits citrate into acetyl-CoA plus oxaloacetate at the cost of one ATP. This freshly liberated acetyl-CoA feeds directly into fatty acid synthase.
Step 4: The remaining choices belong elsewhere: citrate synthase and aconitase work within the mitochondrial cycle, and malic enzyme supplies reducing power as NADPH. Only ATP citrate lyase cleaves citrate for lipogenesis.
\[\boxed{\text{ATP citrate lyase}}\]
Step 2: The cell solves this with the citrate shuttle. Acetyl-CoA is first packaged as citrate by joining oxaloacetate, carried out to the cytosol, and there it must be unpacked again to release the acetyl-CoA.
Step 3: The unpacking step in the cytosol is performed by ATP citrate lyase, which splits citrate into acetyl-CoA plus oxaloacetate at the cost of one ATP. This freshly liberated acetyl-CoA feeds directly into fatty acid synthase.
Step 4: The remaining choices belong elsewhere: citrate synthase and aconitase work within the mitochondrial cycle, and malic enzyme supplies reducing power as NADPH. Only ATP citrate lyase cleaves citrate for lipogenesis.
\[\boxed{\text{ATP citrate lyase}}\]
Was this answer helpful?
0
