Question:medium
Urea, creatinine, and nitric oxide are formed from which amino acid?
Urea, creatinine, and nitric oxide are formed from which amino acid?
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A urea-cycle amino acid that also donates the guanidino group for creatine.
Updated On: Jun 23, 2026
- Histidine
- Glycine
- Cysteine
- Arginine
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Identify a single amino acid that is the common precursor of urea, nitric oxide, and creatine/creatinine.
Step 2: In the urea cycle, arginine is split by arginase into urea and ornithine, directly generating urea.
Step 3: Nitric oxide synthase converts arginine to citrulline and nitric oxide, and the guanidino group of arginine is transferred onto glycine to begin creatine synthesis (creatinine being its end product).
Step 4: Only arginine feeds all three pathways, so the other choices are excluded. \[\boxed{\text{Arginine}}\]
Step 2: In the urea cycle, arginine is split by arginase into urea and ornithine, directly generating urea.
Step 3: Nitric oxide synthase converts arginine to citrulline and nitric oxide, and the guanidino group of arginine is transferred onto glycine to begin creatine synthesis (creatinine being its end product).
Step 4: Only arginine feeds all three pathways, so the other choices are excluded. \[\boxed{\text{Arginine}}\]
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