AMINO-ACIDS 159 



Alanine (a-amino-propionic acid) 

 CH3CHNH2CQOH 



Serine (a-amino- /3-oxypropionic acid) 

 CH2OHCHNH2COOH 



Cystine (Di-a-amino- /3-thiopropionic acid) 

 CH2— S— S— CH2 



Lysine (containing 2 NH2 groups) 



CH2NH2CH2CH2CH2CHNH2COOH 



