第二十章 核苷、核苷酸和核酸 Nucleosides, nucleotides and nucleic acids
第二十章 核苷、核苷酸和核酸 Nucleosides, Nucleotides, and Nucleic Acids
核酸中的碱基( Base in nucleic acids) Nucleic acid DNA—— Deoxyribonucleic acid RNA--Ribonucleic acid basel basel 0、|- glycosidic bond -β glycosidic bond < ribose 2-deoxy-ribosel o OH basel basel OH RNA DNA
核酸中的碱基(Base in Nucleic Acids) DNA——Deoxyribonucleic acid RNA——Ribonucleic acid Nucleic acid base O O O P O O O- base O O O P O O- base O O O P O O O- base O O O P O O- OH OH RNA DN A β-glycosidic bond β-glycosidic bond ribose 2-deox y -ribose
核酸中的碱基 Base in nucleic acids) Nucleoside base sugar Nucleotide= base sugar phosphate Nucleic acid polynucleotide Nucleotide sequence= Base sequence The bases in dna and rna NH NH 2 NH NH NO Adenine(A) Guanine(G)Cytosine( C) Thymine(r) Uracil(t (in DNA) (in RNA) Purine imidine
核酸中的碱基(Base in Nucleic Acids) Nucleoside = base + sugar Nucleotide = base + sugar + phosphate Nucleic acid = polynucleotide Nucleotide sequence = Base sequence The bases in DNA and RNA N N N H N NH 2 NH N N H N O NH 2 A denine(A ) Guanine(G) Purin e N N H NH 2 O NH N H O O NH N H O O Cytosine(C) Thy mine(T) U racil( U ) Pyrim idine (in DNA) (in RNA)
核酸中的碱基( Base in nucleic acids) Why DNa contains T instead of U? 2 NH n tautomerization NH H,O NH NO Cytosine(C Uracil(U) Thymine(t) Base pairing in dna:A=T,G≡T— double helix H N-H H H一 sugar N sugar sugar O H—N sugar H thymine adenine cytosine guanine
核酸中的碱基(Base in Nucleic Acids) Why DNA contains T instead of U? N N H NH 2 O Cytosine(C) NH N H O O Uracil(U) NH N H NH O tautomerization H 2 O NH N H O O Th y mine(T) Base pairing in DNA: A = T, G ≡ T —— double helix N N O O N N N N N N N O N N N N H H H N H sugar sugar H H O H N H sugar sugar thy mine adenine cytosine guani n e
核酸中的碱基( Base in nucleic acids) 思考题:嘌呤和嘧啶都存在互变异构的变化,请 尝试写出它们各自的互变异构结构,并回答这 种互变异构对于碱基配对将产生什么影响?pH 改变对于碱基的配对有无影响,为什么? H N-H……O、N sugar sugar sugar sugar C…… namine adenine cytosine guanine
核酸中的碱基(Base in Nucleic Acids) 思考题：嘌呤和嘧啶都存在互变异构的变化，请 尝试写出它们各自的互变异构结构，并回答这 种互变异构对于碱基配对将产生什么影响？pH 改变对于碱基的配对有无影响，为什么？ N N O O N N N N N N N O N N N N H H H N H sugar sugar H H O H N H sugar sugar thy mine adenine cytosine guani n e