The Chemical Basis of Life 



15 



Heterocyclic amino acids, 

 Proline 



Hydroxyproline 



Histidine 



CO— OH 



/ 



CH 2 — CH 



/ \ 



CH 2 NH 



/ 



CH 2 



CO— OH 

 CH 2 — CH 



y \ 



HOCH NH 



\/ 



CH 2 



H CO— OH 



\ / 



H C— CHo— CH 



XN N X NH 2 



IN 



Tryptophane 



NH- 



CO— OH 



CH- 



// 



// 

 CH 



\ 



CH==CH 



-CH 



\ / 



-C C— CH 2 — CH 



\ / \ 



C HH 2 



/ 



Anhydrides : 



Leucine anhydride 



CH 3 CO— NH CH 3 



^ / \ / 



CH— CH 2 — CH CH— CHo— CH 



/ \ / \ 



CH 3 NH— CO CH 8 



Because of their frequent occurrence in living 

 tissues, the formulas of the following substances 

 should also be given. 



