Uric acid is the final product of

Uric acid is the final product of

• A. Allantoin metabolism
• B. Amino acid metabolism
• C. Purine metabolism
• D. The urea cycle

Answer: (C)

Uric acid is the end product of purine metabolism in humans. Purines from nucleotides are degraded in a stepwise fashion—from AMP and GMP down to adenosine, inosine, hypoxanthine, and xanthine—with xanthine oxidase catalyzing the last steps to form uric acid. Humans lack functional uricase, so uric acid isn’t further converted to allantoin and is excreted in urine. This distinguishes it from allantoin metabolism (which occurs in species with uricase), and from the other two options: amino acid metabolism pertains to different nitrogenous substrates, and the urea cycle disposes of ammonia as urea rather than handling purine breakdown.

Uric acid is the end product of purine metabolism in humans. Purines from nucleotides are degraded in a stepwise fashion—from AMP and GMP down to adenosine, inosine, hypoxanthine, and xanthine—with xanthine oxidase catalyzing the last steps to form uric acid. Humans lack functional uricase, so uric acid isn’t further converted to allantoin and is excreted in urine. This distinguishes it from allantoin metabolism (which occurs in species with uricase), and from the other two options: amino acid metabolism pertains to different nitrogenous substrates, and the urea cycle disposes of ammonia as urea rather than handling purine breakdown.