扬州大学：《生物化学 Biochemistry》课程教学课件（讲稿）06 Nucleotides and Nucleic Acids

Nucleotides and Nucleic Acids

Nucleotides and Nucleic Acids

KeyPrinciplesNucleicacidsarebothrepositoriesandfunctional expressionofbiologicalinformation.Thetransmissionofbiological informationreliesonmolecularcomplementarity.Nucleosidetriphosphatesoccupya central rolein cellularmetabolismserving as an energy currency and as important regulatory signals

Key Principles  Nucleic acids are both repositories and functional expression of biological information.  The transmission of biological information relies on molecular complementarity.  Nucleoside triphosphates occupy a central role in cellular metabolism, serving as an energy currency and as important regulatory signals

1.SomebasicdefinitionsandconventionsNucleotideshaveavarietyofrolesincellularmetabolism-energycurrencyinmetabolictransactions-essentialchemicallinksintheresponseofcellsto hormones and otherextracellular stimuli-structuralcomponentsofanarrayofenzymecofactorsandmetabolicintermediates-constituents of nucleic acids:deoxyribonucleicacid (DNA)and ribonucleic acid (RNA)

1. Some basic definitions and conventions  Nucleotides

DifferentClassesof NucleicAcidsThetwomajorclassesofnucleicacidsareDNAandRNADNA has only onebiological role: store information.Theinformationtomakeallthefunctionalmacromoleculesofthecell ispreserved inDNA. RNA has a number of important biological functions. Its centralone is transferring information from DNA to protein

Different Classes of Nucleic Acids  The two major classes of nucleic acids are DNA and RNA.  DNA has only one biological role: store information. The information to make all the functional macromolecules of the cell is preserved in DNA.  RNA has a number of important biological functions. Its central one is transferring information from DNA to protein

The function of DNAgene = a segment of a DNA molecule that containsthe informationrequiredforthe synthesisof afunctional biological product, whether protein orRNAonlyknownfunctionsofDNA:-storageofbiologicalinformationtransmissionofthat informationtothenextgeneration

 The function of DNA

Thefunctionand several classesofRNAribosomalRNAs(rRNAs)=componentsofribosomes-messengerRNAs(mRNAs)=intermediatesinprotein synthesistransferRNAs(tRNAs)=adaptermoleculesthat translatethe information inmRNAintoaspecific amino acid sequencenoncodingRNAs(ncRNAs)=widevarietyoffunctions

 The function and several classes of RNA

NucleotidesandNucleicAcidsHaveCharacteristicBasesandPentosesnucleotideshavethreePurine orcomponents:pyrimidinebaseanitrogenousbasePhosphate(pyrimidine orPentosepurine)-apentoseOHOH(a)-1+phosphatesnucleoside=theHCHCmoleculewithouta(b)PurinePyrimidinephosphate group

Nucleotide Nitrogenous Basesmajor purine bases:-adenine(A)=inDNAand RNA- guanine (G)= in DNAandRNAAdenineGuaninePurinesmajorpyrimidine bases:-cytosine(C)=inDNAandRNAthymine (T) = only inUracilCytosineThymineDNA(RNA)(DNA)Pyrimidinesuracil(U)=onlyinRNA

NucleotideandNucleicAcidNomenclatureTable 8-1 Nucleotide and Nucleic Acid NomenclatureBaseNucleosideNucleotideNucleic AcidPurines:RNAAdenosineAdenylate碱基名称英文全称读音DNAAdenineDeoxyadenosineDeoxyadenylate腺嘌岭Adenine/'aedani:n/Purines:RNAGuanylateGuanosineGuanineDeoxyguanosineDNADeoxyguanylate胸腺嘧啶Thymine/eaimi:n/Pyrimidines:CytidineCytidylateRNADNACytosineDeoxycytidineDeoxycytidylate鸟嘌岭GuanineI'gwa:nin/Pyrimidines:ThymidineorThymidylateordeoxythymidylateDNA胞嘧啶Cytosine/'sartasi:n/ThyminedeoxythymidinePyrimidines:UridineUridylateRNAUracil

Nucleotide Pentosestwokinds ofpentoses:E-2'-deoxy-d-ribose=OHin DNA-OHH-OHD-ribose=inRNA5CH2OH(a)Aldehydeβ-Furanoseboth areintheirβ-furanose(closedfivemembered ring)form