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THE CHEMICAL COMPOSITION OF THE BODY 



H 



c 



HC 



H NH 2 



I I 

 -C-C-C-COOH 



II I I 

 CH H H 



C NH 

 H 



Tryptophane. 

 (Indol amino proprionic acid.) 



CH 3 H NH 2 



I I I 

 H- C-C-C-COOH 



I I I 

 CH 3 H H 



Leucine. 

 (a-amino isobutylacetic acid.) 



H NH 2 



I I 

 HC=C-C-C-COOH 



I I I I 

 HN N H H 



CH 3 NH 2 



H-C-C-COOH 



I I 

 CH 3 H 



Valine. 

 (a-amino isovalerianic acid.) 



NH, 



C 

 H 



(amino succinic acid.) (a-amino normal glutaric 



acid). 



H H H NH 2 



I I I 



H -N -C -C -C -C - COOH 



III I 



NH=C H H H H 



NH, 



Histidine. 

 (a-amino /?-imidazol proprionic acid.) 



NH 2 H H H NH 2 



Arginine. 

 (guanidine a-amino valerianic acid.) 



H-C-C-C-C-C- COOH 



H H H H H 



Lysine. 

 (a-e-diamino caproic acid.) 



The amino acids belong either to what is known in organic chemistry as 

 the aliphatic, carbocyclic, or heterocyclic series; that is, they are derivations 

 either of the hydrocarbons, of benzene or of closed-ring compounds not 

 composed wholly of carbon atoms, but in which one or more of the links 

 in the closed chain are supplied by other polyvalent elements (in the proteins 

 by nitrogen). Thus tyrosine and phenylalanine are carbocyclic compounds; 

 histidine, proline, and tryptophane are heterocyclic compounds, and the 

 remaining members of the list are aliphatic derivatives. 



Of the elements of the protein molecule, nitrogen is by far the most 



