3核苷 O NH2 (nucleoside) HO-CR2o HO-CH HO-CH2 o HO-CH. ”2 腺嘌呤核苷 鸟嘌呤核苷 胞嘧啶核苷 尿嘧啶核苷 2 NH2 CH HN N HO-CH, OH 腺嘌呤脱氧核苷鸟嘌呤脱氧核苷胞嘧啶脱氧核苷胸腺嘧啶脱氧核苷 核苷(上)与脱氧核苷(下)1.3 核苷 (nucleoside) N N N 9 N NH2 1 O OH H H H H CH2 H HO HN N N O H2N N 9 1 O OH H H H H CH2 H HO O OH H H H H CH2 H HO 1 N 1 N NH2 O O OH H H H H CH2 H HO 1 N 1 HN O O 腺嘌呤脱氧核苷 鸟嘌呤脱氧核苷 胞嘧啶脱氧核苷 胸腺嘧啶脱氧核苷 N N N 9 N NH2 1 O OH OH H H H CH2 H HO HN N N O H2N N 9 1 O OH OH H H H CH2 H HO O OH OH H H H CH2 H HO 1 N 1 N NH2 O O OH OH H H H CH2 H HO 1 N 1 HN O O 腺嘌呤核苷 鸟嘌呤核苷 胞嘧啶核苷 尿嘧啶核苷 CH3 核苷（上）与脱氧核苷（下）