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Chapter 27 Nucleosides, Nucleotides, and Nucleic Acids I Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall Organic Chemistry 4 th Edition Paula Yurkanis Bruice Nucleic Acids In nucleic acid, the phosphate group is phosphodiester The Bases in Nucleic Acids Adenine, guanine, cytosine, and thymine are found in DNA Adenine, guanine, cytosine, and uracil are found in RNA Nucleosides = Base + Sugar Nucleotides = Base + Sugar + Phosphate Different Forms of Nucleotides The energy released from ATP hydrolysis is used to drive the phosphorylation of D-gluose (coupled reactions) ATP as a Chemical Energy Source Breakage of the Phosphoanhydride Bond in ATP [...]...Without ATP, the OH– group cannot be displaced This reaction does not occur without ATP because of the poor leaving group Phosphoryl Transfer Reaction Mechanism I Phosphoryl Transfer Reaction Mechanism II Phosphoryl Transfer Mechanism III Pyrophosphate can be further hydrolyzed to phosphate . OH – group cannot be displaced This reaction does not occur without ATP because of the poor leaving group Phosphoryl Transfer Reaction Mechanism I Phosphoryl