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