C00 C00 H H NH3 CH3 CH3 L-Alanine D-Alanine (a) All objects have mirror images.Like many biomolecules, amino acids exist in mirror-image forms (stereoisomers) Only the L-isomers of amino acids commonly occur in nature All objects have mirror images. Like many biomolecules, amino acids exist in mirror-image forms (stereoisomers). Only the L-isomers of amino acids commonly occur in nature