Nonpolar,aliphatic R groups coo C00 coo HN-C-H HgN-C-H HN-C-H 五 CH3 CH CHs CHa Glycine Alanine Valine COO C00 C00 HgN-C-H HaN-C-H HaN-C-H CH2 CH2 H-C-CH3 CH CH2 CH2 CHs CH3 CH3 CH3 Leucine Methionine Isoleucine