Uric acid is a product of catabolism of which purines?

• A. Adenosine and Guanine
• B. Adenine and Guanine
• C. Cytosine and Uracil
• D. Guanine and Thymine

Answer: (A)

Uric acid is the end product of purine breakdown. Purines are the two bases adenine and guanine. When these bases are degraded in humans, they are ultimately converted through intermediate steps to uric acid, which is then excreted in urine. Adenosine is a nucleoside (adenine attached to ribose), so while it relates to purine metabolism, the question focuses on the purine bases themselves. The other bases listed (cytosine, uracil, thymine) are pyrimidines, not purines, so they aren’t the sources of uric acid in this catabolic pathway. Therefore, the purines that yield uric acid are adenine and guanine.