Two purine bases: Sir becomes hypoxanthine, then xanthine and finally uric acid, which are excreted. Uric acid or purine ring structure is nitrogen-containing waste. Hypoxanthine and xanthine are also purine bases, but they do not participate in the synthesis of DNA or RNA and are used as coenzymes of oxidoreductase. There are two kinds of pyrimidine bases: ammonia (NH3), carbon dioxide (CO2), β -alanine (catabolite of cytosine) and β -aminobutyric acid (catabolite of thymine). After base decomposition, pyrimidine ring is no longer retained. β -alanine and β -aminoisobutyric acid are also amino acids, but they are both β-amino acids and do not participate in protein synthesis. Deoxyribose: Like other carbohydrates, it enters the normal metabolic pathway, and the products are carbon dioxide (CO2) and water. Feng Jiao preserved wool phosphate: it is no longer decomposed and directly used for other anabolism. Such as nucleotides, ATP or other products. It can also be used as inorganic phosphate and as a buffer system to maintain normal pH value of human body.