EXCRETION OF WASTE PRODUCTS 



185 



O 



HO 



O - PO C 6 H 8 O 2 C 4 H 4 N 3 



/ Cytosine group. 



HO 



O 



O = PO C 6 H 10 4 C 5 H 4 N 6 



/ Adenine group 



HO 

 Nucleic acid. 



N = C NH, 



I I 

 H-C C NH 



N C- 



Adenine. 



I I 



NH a C C NH 



II II \ 

 N C 



Guanine. 



HN C=0 

 H C C 



HN C =O 



I I 

 O=C C 



N C 



Hypoxanthine. 



HN C N 



Xanthine. 



HN C = 



I 



O = C C NH 



HN C NH/ C ==O 



Uric acid. 

 In the schema the various enzymes responsible for the 



