446 APPENDIX 



If the ring contain less than six carbon atoms it is called heterocyclic. 

 One of the most important of these is Pyrrhol 



C C 



I! II 

 c c 



\y 



N 

 H 



which occurs linked to a benzene ring in certain important constituents of 

 the protein molecule. 



NITROGEN-CONTAINING COMPOUNDS 



Ammonia. The three-handed Nitrogen by linking with three hydro- 

 gens forms Ammonia, 



H 



H N H 



If one of these hydrogens is removed, Amidogen, which can link with 

 other molecules, is produced. 



Amino Acids. If one of the hydrogen atoms in the radical of an acid 

 is replaced by amidogeii a mon-amino acid is formed, thus : 



H O 



H, | || 



\N C C H Aniino acetic acid. 



H 



When two hydrogen atoms are thus replaced, a di-amino acid is produced 

 NH 2 NH 2 O 



H C C C O H Di-amino propionic acid. 



I I 

 H H 



Amides. If the ainidogen molecule takes the place of the hydroxyl in 

 the carboxyl of an acid an amide results, thus : 



O 

 H C O H Formic acid. 







II /H 



H C N< Formamide. 

 X H 



