coo C00 H H NHa C00 COO C00 C00 HaN- C-H H-GNH, HN-C-H H-C-NH CH CHa CHa CHa CH CHa L-Alanine D-Alanine L-Alanine D-Alanine L-Alanine DAlanine (a) (b) (c) Because the resulting amino acid contains one positive and one negative charge,it is a neutral molecule called a zwitterion.Amino acids are also chiral molecules.With four different groups attached to it,the a-carbon is said to be asymmetric.The two possible configurations for the a- carbon constitute nonidentical mirror image isomers or enantiomers(对映体)
• Because the resulting amino acid contains one positive and one negative charge, it is a neutral molecule called a zwitterion. Amino acids are also chiral molecules. With four different groups attached to it, the a-carbon is said to be asymmetric. The two possible configurations for the acarbon constitute nonidentical mirror image isomers or enantiomers(对映体)
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
The a-amino carboxylic acids (amino acids can be of two stereoisomers R H NH3" C00 c00 Lisomer D isomer
The a-amino carboxylic acids (amino acids) can be of two stereoisomers
C00 C00 HN-C-H H- NH3 三。 CH3 CH3 L-Alanine D-Alanine (b)
C00 C00 HN-C-H H-C-NH3 CH3 CH3 L-Alanine D-Alanine (c)