生物化学(1).ppt

1,生物化学（1）杨缜Office:实验楼S-329Tel.:26534152e-mail:zyang,2,Aboutthiscourse,WhatisBiochemistry?Whyisthiscoursesoimportant?Howisthiscourseorganized?,3,英文网站,深大主页教学服务网上课程多媒体教学资源本校教师开发的教学资源生物化学英文学习网站,参考教材LehningerPrinciplesofBiochemistry,4thedition(2005)DavidL.NelsonandMichaelM.CoxW.H.FeeemanandCompany,主要教材生物化学第三版（上册）,4,Contents,Chapter1.GeneralintroductionChapter2.CarbohydratesChapter3.LipidsChapter4.Aminoacids,peptidesandproteinsChapter5.ProteinstructureChapter6.EnzymesChapter7.NucleotidesandnucleicacidsChapter8.Vitaminsandcoenzymes,5,Chapter1.GeneralIntroduction,Livingorganismsvs.inanimateobjectsBiomoleculesWaterandbufferExperimentalapproachandmethodsusedinbiochemistry,6,I.Livingorganismsvs.inanimateobjects,ChemicalcomplexityandorganizationCapacityforextracting,transforming,andusingenergyfromenvironmentsCapacityforself-replicationandself-assembly,7,II.Biomolecules,MajortypesofbiomoleculesBiomolecularhierarchyChemicalprinciplesgoverningpropertiesofbiomolecules,8,MolecularComponentsofanE.ColiCell,9,NormalChemicalCompositionforaManWeighing65kg,Water61.6%,40kg,Protein17.0%11kg,Fat13.8%,9kg,Minerals6.1%,4kg,Carbohydrate1.5%,1kg,10,1.Majortypesofbiomolecules,Biomoleculesaremacromoleculesthatarepresentinlivingorganismswithbiologicalactivities.,11,Elementarycompositionofthehumanbody(dryweightbasis),C:60%,O:20%,H:10%,N:8.5%,Ca,P,KSNaClMgFeMnI,Ca,12,2.Biomolecularhierarchy,Inorganicprecursors(无机物前体)18-64daltonsCO2,H2O,NH3,N2,NO3-,Metabolites(代谢物)50-250daltonse.g.pyruvate,citrate,Buildingblocks100-350daltonse.g.aminoacids,nucleotides,Mteins,lipids,Supramolecularcomplexes106-109daltonse.g.ribosomes,chromosomes,Organellese.g.nucleus,mitochondria,chloroplasts,Thecell,Unitoflife,13,Structuralhierarchyinthemolecularorganizationofcells,14,AclassicexperimentontheabioticoriginoforganicbiomoleculesbyMillerandUrey(1953),Products:Gasphase:CO,CO2Liquidphase:aminoacids,aldehyde,HCN,etc.,Prebioticevolutionperiod:BiomoleculeswerefirstarosebychemicalevolutionLighteningdischargeselectricalenergyVolcanoesheatenergy,15,3.Chemicalprinciplesgoverningpropertiesofbiomolecules,1).Elementarycompositions(元素组成)2).Molecularstructures(分子结构)3).Stereospecificinteractions(立体专一的相互作用)4).4typesofnoncovalentinteractions(非共价作用)5).5typesofchemicalreactionsincells(细胞内的化学反应),Chemistryisthelogicofbiologicalphenomena.,16,1).BiomoleculesarecompoundsofC,CovalentlinkagewithH,O,N,C:4mostabundantelementsCskeletons(骨架):linear,branched,cyclicFunctionalgroups(功能团):,17,Composition(组成)e.g.,C4H4O4Constitution(构造)e.g.,HOOC-CH=CH-COOHConfiguration(构型)changedbybondbreakageConformation(构象)changedbybondrotation,2).Molecularstructures(分子结构),P.3,18,马来酸,富马酸,视网膜醛,19,StereoisomersarecompoundsthathaveSamecomposition(相同组成)Differentconfigurations(不同构型)StereoisomersarecausedbythepresenceofDoublebonds:cis-transisomers(顺反异构)Chiralcenters:nchiralcarbons2nmaxstereoisomerse.g.C*ABXYe.g.C*HX(CH3)-C*HY(CH3)TwotypesofstereoisomersEnantiomers(对映异构体)MirrorimagesSamephysicalandchemicalpropertiesDiastereomers(非对映异构体)Non-mirrorimagesDifferentphysicalandchemicalproperties,Stereoisomers(异构体),20,Enantiomersanddiastereomers(对映异构体和非对映异构体),21,PropertiesofStereoisomers,Enantiomers:identicalphysicalandchemicalpropertiesinachiralenvironments,m.p.146o174opK13.232.98,Diastereomers:differentcompounds,differentphysicalandchemicalproperties,m.p.174o174opK12.982.98,对映异构体：性质相同,非对映异构体：性质不同,22,Molecularasymmetry:Chiralandachiralmolecules(手性和非手性分子),C*ABXY,Chiral-notsuperimposableonthemirrorimageAchiral-superimposableonthemirrorimage,Moleculeswithmorethanonechiralcentersmaynotnecessarilybechiral.(有一个以上手性C的分子不一定就是手性分子),*,*,23,香芹酮,24,Enzymesubstrate(酶-底物)Antigenantibody(抗原-抗体)Hormonereceptor(激素-受体),3).Stereospecificinteractions(立体专一的相互作用),25,H-bonds(氢键)Ionicinteractions(离子键)Hydrophobicinteractions(疏水相互作用)vanderWaalsinteractions(范德华力),4).Noncovalentinteractions(四种非共价相互作用),Importance:Determiningtheintra/intermolecularinteractions(决定分子内/分子间的相互作用)Maintainingthe3-dimensionalstructure(维持三维空间结构)Determiningthebiologicalfunction(决定生物功能),26,Stabilizationenergy(kJ/mol),8-21,42,4-8,4,27,Oxidation-reduction(氧化还原反应)Cleavage&formationofC-CbondsInternalrearrangements(内部重排)Grouptransfers(基团转移)Condensations(缩合反应),5).5typesofchemicalreactionsincells(细胞内的五类化学反应),28,Oxidation-Reduction(氧化还原反应),Cleavage&formationofC-Cbonds(C-C键的断裂与形成),Internalrearrangements(内部重排),29,Condensations(缩合反应),-H2O,Grouptransfers(基团转移),30,RoleofwaterUnusualpropertiesofwaterBuffer(缓冲溶液),III.Waterandbuffer,31,1)Wateristhemostabundantsubstanceinlivingsystems.70%oftheweightofmostorganisms2)Waterservesasthemediumoflife.Solutesinwater(apolarsolvent):极性物质:PolarsoluteH-bonds带电荷的物质:Chargedsoluteelectrostaticinteractions非极性物质:Nonpolarcompoundpoorlysoluble两性物质:AmphipathiccompoundmicellesWatercontrolsthepHofcellsandbodyfluids.Waterparticipatesdirectly/indirectlyinallchemicalprocessesinlivingsystems.Directasareactant/aproductIndirectasareactionmedium,1.Roleofwater,32,MembraneStructure,33,Highboilingpointandmeltingpoint(熔点、沸点)Highspecificheat(比热)Highheatofvaporization(蒸发热)Highsurfacetension(表面张力)Highinternalcohesion(内部凝聚力)Highdielectricconstant(介电常数)DensityoficelowerthanthatofliquidwaterOsmosis(渗透作用)StronghydrogenbondingAbilitytoionize,2.Unusualpropertiesofwater,34,Osmosisandthemeasurementofosmoticpressure(渗透作用和渗透压的测量),VantHoffequation:Osmoticpressure=icRT,35,FreshwaterfishRosybarb,SeawaterfishClown,等渗,高渗,低渗,36,Somebiologicallyimportanthydrogenbonds,37,3.Buffer,1).Ionizationofwater(水的电离)2).Dissociationofelectrolyteinwater(电解质在水中的离解)3).Titrationcurves（滴定曲线）4).BufferingagainstpHchange5).Buffersystemsusedinorganisms,38,1).Ionizationofwater（水的电离）,H2O,H+OH-,Keq=,H+OH-,H2O,=1.8x10-16,Kw=H+OH-=H2OKeq=(55.5M)x(1.8x10-16M)=10-14,Equilibriumconstant(平衡常数):,Ionproductofwater(离子积):,pH=-logH+pH+pOH=14,39,2).Dissociationofelectrolyteinwater(电解质在水中的离解),Strongelectrolytes:NaClNa+Cl-,Weakelectrolytes:,Weakacid:,Weakbase:,HA,H+A-,BOH+H+,B+H2O,Ka=,H+A-,HA,logKa=logH+logA-logHA,Dissociationconstant(离解常数),Henderson-Hasselbalchequation,pH=pKa+log,A-,HA,pKa=-logKa,40,R-COOH,R-COO-+H+,R-NH3+,R-NH2+H+,Weakacid(弱酸):,Weakbase(弱碱):,AcidConjugateacidProtondonor,Conjugatebase（共轭碱）BaseProtonacceptor,BaseConjugatebase,Conjugateacid（共轭酸）Acid,Buffersaremixturesofweakacidsandtheirconjugatebases.,41,3).Titrationcurves（滴定曲线）,pH=pKa+log,A-,HA,WhenA-=HA,pH=pKa,42,4).BufferingagainstpHchange,Abuffersystemiscomposedofaweakacidanditsconjugatebase.e.g.HA/A-EachbufferhasitsspecificpKa,andhenceitsspecificbufferingzone.Apolyproticacid(e.g.H3PO4)hasmorethanonedissociableH+,andhencemorethanonepHbufferingzone.Differentbuffersystemsshouldbeselectedfordifferentpurposes.,H3PO4,H2PO4-,HPO42-,PO43-,pKa1,pKa2,pKa3,2.15,6.86,12.4,43,CH3COOH/CH3COO-,H2PO4-/HPO42-,NH4+/NH3,Differentbuffersystems:,44,5).Buffersystemsusedinorganisms,H+HCO3-,H2CO3,CO2(d),CO2(g),Aqueousphase(Bloodincapillaries),Gasphase(Lungairspace),Bicarbonatebuffersysteminbloodplasma,FormaintainingintracellularpH(胞内pH)Phosphatesystem(H2PO4-/HPO42-)HistidinesystemFormaintainingextracellularpH(胞外pH)Bicarbonatesystem(H2CO3/HCO3-),45,IV.Experimentalapproachandmethodsusedinbiochemistry,ThreemajorcomponentsusedinstudyofbiomoleculesGeneralstrategyusedtoanalyzeabiochemicalprocessormetabolicpathway,4