This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Final product of purine metabolism is: \nSelect and explain. \nA. Uric acid, B. Creatinine, C. Xanthine, D. Phoshphates', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Nucleotides are derived from biosynthetic precursors of carbohydrate and amino acid metabolism, and from ammonia and carbon dioxide.The liver is the major organ of de novo synthesis of all four nucleotides.Degradation in humans, however, is only complete for pyrimidines (C, T, U), but not purines (G, A), which are excreted from the body in form of uric acid', 'role': 'assistant'}]