Chapter 9

Chapter 9 - II III I Chapter 9 Nucleic Acids General...

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II. Chapter 9 III. Nucleic Acids I. General structure of nucleic acids (N.A.s) A. N.A.s are polymers of nucleic acids that are linked by the formation of 2 ester bonds by phosphoric acid to make a 3’ to 5’ phosphodiester bond B. Sugars 1. In life, we use D-sugars. 2. -D-ribose (RNA)- has a H on the 2’ C, it lacks an O atom 3. -D-deoxyribose (DNA) has an OH on the 2’ C C. Bases: heterocyclic nitrogenous bases 1. Purines 9 membered ring structures not very water soluble Adenine: 6 amino purine Guanine: 2 amine 6 oxypurine 2. Pyrimidines 6 membered, aromatic ring structure can form many H bonds and therefore are more soluble a. Cytosine: 2 oxy 4 amino pyrimidine (DNA) b. Uracil: 2,4 dioxypyrimidine (RNA) c. Thymine: 2,4 dioxy 5 methylpyrimidine (DNA) D. Nucleic acids can be viewed with levels of structure 1. Primary structure: Order of bases in the polynucleotide sequence 2. Secondary structure: 3-D conformation of the backbone 3. Tertiary structure: Supercoiling of the molecule II. Nomenclature A. Nucleosides nitrogenous base and a sugar covalently linked together (glycosidic linkage) B. Nucleotides nucleoside monophosphate, which is on the 5’ end (base + sugar + phosphate group); repeating units in nucleic acid; has directionality C. nitrogenous bases alone
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III. Nucleic acids have directionality – which is similar to what we see with proteins A. 5’ end : Free Phosphate on the 5’ position of 5 -C sugar B. 3’ end : Free –OH on the 3’ position of 5
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Chapter 9 - II III I Chapter 9 Nucleic Acids General...

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