20 



THE AMINO ACIDS 



CH 3 



I 



CH.NH 9 



I 

 COOH 



Alanine 



CH 9 



CH 



\ 



CH.NH a 



I 

 COOH NH 



Tryptophane 



CH 



x\ 



C CH 



I! I 



C CH 



CH 



CH NH 



x 



CH 2 C - W 

 CH.NH 2 



COOH 



Histidine 



Again valine, leucine and isoleucine are closely re- 

 lated structurally as may be seen from the formulas 

 following. 



CH 3 CH 3 



CH 3 CH 8 



Valine 



Leucine 



Isoleucine 



