128 



The Twenty Amino Acids Found in Proteins (continued) 



ASPARAGINE (asn) 



GLUTAMINE (gin) 



H 2 N— C— CH 2 — CH — COOH 



H 2 N — C — CH 2 — CH 2 — CH — COOH 



NH- 



NH- 



ARGININE (arg) 



LYSINE (lys) 



NH 

 II 

 NH 2 — C— NH— CH 2 — CH 2 — CH 2 — CH— COOH 



NH 2 — CH 2 -CH 2 — CH 2 — CH 2 — CH— COOH 



NH- 



NH- 



HISTIDINE (his) 

 HC C — CH 2 — CH — COOH 



HN^ ^N 

 CH 



NH- 



PHENYLALANINE (phe) 



CH 2 -CH— COOH 



NH- 



TYROSINE (tyr) 



TRYPTOPHAN (trp) 



HO- 



\ 



-CH 2 — CH— COOH 



NH- 



CH 2 — CH — COOH 



NH, 



