The two enantiomers of each amino acid defined by the a-carbon are designated D-and L-forms(d for Dextrorotary右旋, Lfor Levorotary左旋) COO coo C00 CO0 H3N-C-H H--c-NH3H3 N-C-H H--C-NHs CH3 CH CH3 CH3 L-Alanine D-Alanine L-Alanine D-Alanine (c) The horizontal bonds project out of the plane of the paper, the vertical behindThe horizontal bonds project out of the plane of the paper, the vertical behind. The two enantiomers of each amino acid defined by the -carbon are designated D- and L- forms (D for Dextrorotary右旋, L for Levorotary左旋)