THE PROTEINS AND THEIR METABOLISM 



91 



3. Histidin or a-amino fi-iminoazol propionic acid. 

 CH Nil ~\ 



\rar [ Iminoazol radical 

 



C 

 CH 2 

 CIINH 2 Alanin radical 



COOH 



4. .Tryptophan or Indol a-amino propionic acid. 

 CH 



/ \ 

 HC C C CH 2 CHNH 2 COOH 



HC C CH 



\ /\V 



CH NH 



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 

 or complex their structure, possess at least one amino ( NH 2 ) radical and 

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

 amino acid the power of uniting with at least two. other amino acids of 

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



H 



CH 



N 

 \ 



H 



COOH 

 Glycocoll 



H 



\ 



H 



II 



CH, 



III 

 H 



CH, 



CO 



H 



N CH, 



COOH 

 Glycocoll 



H COOH 



Glycyl-glycin 



H0 



