is derived from Greek word, “ proteios ” which means primary or of prime importance. All proteins are polymers of a -amino acids. Amino acids contain amino (–NH ) and carboxyl (–COOH) functional groups. Depending upon the relative position of amino group with respect to carboxyl group, the amino acids can be classified as a , b , g , d and so on.
Only a -amino acids are obtained on hydrolysis of proteins. They may contain other functional groups also. All a -amino acids have trivial names, which usually reflect the property of that compound or its source. Glycine is so named since it has sweet taste (in Greek glykos means sweet) and tyrosine was first obtained from cheese (in Greek, tyros means cheese.) Amino acids are generally represented by a three letter symbol, sometimes one letter symbol is also used.
Structures of some commonly occurring amino acids along with their -letter and -letter symbols are given in Table . . . Glycine Gly G .
Alanine – CH Ala A . Valine* (H C) CH- Val V . Leucine* (H C) CH-CH - Leu L Name of the Characteristic feature Three letter One letter amino acids of side chain, R symbol code Table . : Natural Amino Acids .
. Amino Acids R CH NH a -amino acid (R = side chain) H N R