170 INTERMEDIATE METABOLISM 



These two substances form an essential constituent of 

 nuclei. 



2. Oxidation 'products : — 



Hypoxanthine (oxvpurine) NH CO 



CjH.N.Oor " I I 



CH C--NH. 



N C N^ 



This occurs in all muscular tissue. 



Xanthine (dioxypurine) NH CO 



C.H^N.O^ or I I 



CO C— NH. 



NH — C N^ 



^CH 



CH 



Uric acid (trioxypurine) NH CO 



C^H.N.Ogor ■ I I 



CO C-NH. 



I II >co 



NH C— NH-^ 



Uric acid is the form in which in man purines are excreted, 

 the daily urine containing about 0-75 grm. It is also 

 found in human blood (1-3 mg. per 100 c.c). In gout 

 the amount in the blood is considerably increased and 

 large crystalhne deposits are formed in the joints. 



3. Methyl derivatives. — Purine bodies occur combined 

 with the CH3 group, as caffeine in coffee, as theophylli7ie 

 in tea, and as theobromine in cocoa. 



Pyrimidine Bases 



These are single-ring nitrogen bases consisting of a 

 three-carbon-atom chain with 07ie urea group. 



