Lecture Slides_ch08_02 - 8| Nucleotides and Nucleic Acids \u00a9 2017 W H Freeman and Company CHAPTER 8 Nucleotides and Nucleic Acids Learning goals \u2022

Lecture Slides_ch08_02 - 8| Nucleotides and Nucleic...

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8| Nucleotides and Nucleic Acids © 2017 W. H. Freeman and Company
CHAPTER 8 Nucleotides and Nucleic Acids Biological function of nucleotides and nucleic acids Structures of common nucleotides Structure of double-stranded DNA Structures of ribonucleic acids Denaturation and annealing of DNA Chemistry of nucleic acids; mutagenesis Learning goals :
Nucleic acids are polymers of nucleotides used for: storage of genetic info (DNA) transmission of genetic info (mRNA) processing of genetic information (ribozymes) protein synthesis (tRNA and rRNA) Nucleotides are also used in the monomer form for cellular functions: energy for metabolism (ATP) enzyme cofactors (NAD + ) signal transduction (cAMP) Functions of Nucleotides and Nucleic Acids
Nucleotides and Nucleosides Nucleotide = nitrogeneous base pentose phosphate Nucleoside = nitrogeneous base pentose Carbon AND nitrogen atoms on the nitrogenous base are numbered in cyclic format. Carbons of the pentose are designated N’ to alleviate confusion.
Phosphate Group Negatively charged at neutral pH Typically attached to 5’ position Nucleic acids are built using the 5’-triphosphates version of the nucleotide. ATP, GTP, TTP, CTP Two of the three phosphates used for building nucleic acids form a leaving group, and completed nucleic acids contain one phosphate moiety per nucleotide. May be attached to other positions for specialized function
Other Nucleotides: Monophosphate Group in Different Positions
Pentose Forms Differ in Some Nucleic acids and Nucleotides -d-ribofuranose in RNA -2’-deoxy-d-ribofuranose in DNA Different puckered conformations of the sugar ring are possible.
Nitrogenous Bases Derivatives of pyrimidine or purine Nitrogen-containing heteroaromatic molecules Planar or almost planar structures Absorb UV light around 250 270 nm
Pyrimidine Bases Cytosine, adenine , and guanine are found in both DNA and RNA. Thymine is found only in DNA. Uracil is found only in RNA. All are good H-bond donors and acceptors. Neutral molecules at pH 7
Nomenclature TABLE 8-1 Nucleotide and Nucleic Acid Nomenclature Base Nucleoside Nucleotide Nucleic acid Purines Adenine Adenosine Deoxyadenosine Adenylate Deoxyadenylate RNA DNA Guanine Guanosine Deoxyguanosine Guanylate Deoxyguanylate RNA DNA Pyrimidines Cytosine Cytidine Deoxycytidine Cytidylate Deoxycytidylate RNA DNA Thymine Thymidine or deoxythymidine Thymidylate or deoxythymidylate DNA Uracil Uridine Uridylate RNA Note: “Nucleoside” and “nucleotide” are generic terms that include both ribo- and deoxyribo- forms. Also, ribonucleosides and ribonucleotides are here designated simply as nucleosides and nucleotides (e.g., riboadenosine as adenosine), and deoxyribonucleosides and deoxyribonucleotides as deoxynucleosides and deoxynucleotides (e.g., deoxyriboadenosine as deoxyadenosine). Both forms of naming are acceptable, but the shortened names are more commonly used. Thymine is an exception; “ribothymidine” is used to describe its unusual occurrence in RNA.

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