练习2:根据氨基酸通式,写出下面四种氨基酸的R基: H H2N-C-C-- OH HNC-C-0 H H2NC-- C—oH H2NC-c—oH CH2 H CH CH3 CH3 CH3 丙氨酸 甘氨酸 缬氨酸 CH3 CH3 亮氨酸 CH2 R基分别是:—H, CH-CH3,=CH CH CH3 CH3 CH3CH CH3 CH3 练习2:根据氨基酸通式,写出下面四种氨基酸的R基： —H, ，—CH3 ， CH2 CH3 CH3 CH H2N—C— C— OH H O H 甘氨酸 缬氨酸 丙氨酸 H2N—C— C— OH H O CH2 CH3 CH3 CH H2N—C— C— OH H O CH3 H2N—C— C— OH H O CH CH3 CH3 亮氨酸 R基分别是: