Question:
The urea cycle occurs in which of the following organs?
The urea cycle occurs in which of the following organs?
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Think of the only organ with all five enzymes that detoxify ammonia.
Updated On: Jun 24, 2026
- Liver
- Intestine
- Brain
- Kidney
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Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Recall the purpose of the urea cycle. It converts toxic ammonia (NH3), produced mainly from amino acid catabolism, into urea for safe excretion.
Step 2: Identify the organ. The complete set of urea cycle enzymes is expressed only in the liver, where ammonia is detoxified to urea.
Step 3: Note the cellular compartments. The first two steps (carbamoyl phosphate synthetase I and ornithine transcarbamoylase) occur in the hepatocyte mitochondria, and the remaining steps (argininosuccinate synthetase, argininosuccinate lyase, arginase) occur in the cytosol.
Step 4: Exclude the other organs. The intestine, brain, and kidney lack the full enzyme complement; the kidney handles ammonia largely via glutamine and direct excretion, not the complete urea cycle.
Conclusion: The urea cycle occurs in the liver, so the correct answer is option 1.
Step 2: Identify the organ. The complete set of urea cycle enzymes is expressed only in the liver, where ammonia is detoxified to urea.
Step 3: Note the cellular compartments. The first two steps (carbamoyl phosphate synthetase I and ornithine transcarbamoylase) occur in the hepatocyte mitochondria, and the remaining steps (argininosuccinate synthetase, argininosuccinate lyase, arginase) occur in the cytosol.
Step 4: Exclude the other organs. The intestine, brain, and kidney lack the full enzyme complement; the kidney handles ammonia largely via glutamine and direct excretion, not the complete urea cycle.
Conclusion: The urea cycle occurs in the liver, so the correct answer is option 1.
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