1. Lectures 12: Nucleotide Structure Reading Assignment: Chapter 35, pgs. 375-385; Harper’s Biochemistry (25 th edition). Objectives: To understand the chemical nature of the basic components that comprise DNA and RNA in human cells. I. Components of Nucleotides A. nitrogenous bases 1. pyrimidines 2. purines 3. Major forms Keto Amino B. five carbon sugars 1. D-ribose 2. 2-deoxy-D-ribose C. phosphoric acid II. Linkage of a nitrogenous base to a five carbon sugar - nucleoside A. N-glycosyl linkage 1. pyrimidine: N-1 of base to C-1= of sugar 2. purine; N-9 of base to C-1= of sugar

2. III. Linkage of a phosphate to a nucleoside - nucleotide A. phosphate added at 5= position of sugar 1. nucleotide monophosphate 2. nucleotide diphosphate 3. nucleoside triphosphate IV. Internucleotide linkage A. 3'-5' phosphodiester bridge