THE PROTEINS AXD THEIR METABOLISM 



91 



3. Histidin or a-aniino $-iminoazol propionic acid. 

 CH XII 1 

 || \r-TT r Iminoazol radical 



c xv c *] 



CH, 



I 

 CHXII, Alanin radical 



I 



coon 



4. Tryptophan or Indol or-amino propionic acid. 

 CII 



/ \ 

 HC C C CII.. CIIXH, COOH 



I II II P 



HC C CH 



\ /\/ 

 CH XH 



Indol 

 radical 



Alanin 

 radical 



The Role of Amino Acids in the Structure of the Protein 



Molecule 



From the above it is seen that all the amino acids, no matter how simple 

 r complex their structure, possess at least one ammo ( XH 2 ) radical and 

 .it least one acid ( COOH) radical. These two radicals impart to each 

 iiiiiino acid the power of unithur with at least two other amino acids of 

 Hinilar or different structure, forming what are known as peptids. 



II 



II 



11 



H 



\ 



II 



X CII, 



coon 



Glvc-ocoll 



III 



II 



Clio N 



I \ 



II 



CO X OH. 



/ I 

 II COOH 



Glycyl-glycin 



ILO 



