C N HC O HO P O CH C N CH2 N C N O HO Sugar OH HO consists of Nitrogenous Bases Purines have a double ring structure. H C N N C CH C HC N N H Adenine (A) Guanine (G) Five-Carbon Sugars Pyrimidines have a single ring. N HC Cytosine (C) H C N Deoxyribose {de-, without; oxy-, oxygen} Ribose HOCH2 OH O Phosphate HOCH2 O OH CH HO P HO CH HO Thymine ....