604 



METABOLISM 



Two cysteine molecules united at the " S " groups give cystine. 

 NH., 



OILS - CH 



COOH 



NH, 



3. Phenylalanine has a C 6 H 6 (phenyl) group, CH 2 C 6 H 5 -CH 



\ 



COOH 

 NH 



4. Tyrosine has a C 6 H 4 OH (phenol) group. CH,C C H 4 OH - CH 





COOH 



C 



\ 



5. Tryptophane has a C 6 H 4 CH (indole) group: 



\ / 

 NH 



C CH 2 - CH - NH 2 - COOH. 



/ \ 

 C.H 4 CH 



\ / 

 NH 



CH 



/ \ 



N NH 



I ! 



6. llistidine has a CH C - (imidazole) group: 



CH 



/ \ 



N NH 



I ! 



CH = C.CH 2 . CH. NH 3 -COOH. 



The last two are also called keterocyclic compounds, of which there 

 is another, viz.; 



Proline (and oxyproline), which is a-pyrrolidine carboxylic acid: 



CH 2 CH 2 



I ' I 



CH 2 CH.COOH 



\ / 

 NH 



Other amino acids are: 



(1) Valine 

 Leucine 

 Isoleticine 

 thus : 



CH. CH, CH, CH 3 CH 3 C 2 H 5 



\ / \ / \ / 



CH CH CH 



CH.NH 2 

 COOH 



(valine.) 



CH 2 



I 

 CH.NH 2 



COOH 



(leucine) 



CH.NH 2 

 COOH 



(isoleucine) 



