Sec 1:Classification and stereochemistry of amino acids ■Standard Amino Acids OTwenty standard a-amino acids. .Differ in side-chain characteristics: >-H or alkyl >contains an -OH >contains sulfur >contains a nonbasic nitrogen >has -COOH >has a basic nitrogenSec 1: Classification and stereochemistry of amino acids ◼Standard Amino Acids ⚫Twenty standard -amino acids. ⚫Differ in side-chain characteristics: ➢-H or alkyl ➢contains an -OH ➢contains sulfur ➢contains a nonbasic nitrogen ➢has -COOH ➢has a basic nitrogen