碱基、核苷、核苷酸的概念和关系 Pyrimidines Purines C AI G HC Cytosine Thymine Uracil Adenine Guanine Nitrogenous Phosphate base 核苷磷酸 Pentose sugar 戊糖碱基 HOCH,/O OH HOCHO OH -P-0 O HO Ribose (in rNA) Doxyribose(in DNA)碱基、核苷、核苷酸的概念和关系 Nitrogenous base Pentose sugar HOCH2 H OH Doxyribose (in DNA) HOCH2 HO OH Ribose (in RNA) Phosphate Pyrimidines Cytosine Thymine Uracil C T U Purihes Adenine Guanine A G 核酸 核苷 磷酸 戊糖 碱基