分子生物学知识点

分子生物学知识点WhatwelearnedlastclassTeachingarrangementofthiscourseDefinitionofMolecularBiologyGoalsofMolecularBiologyMajoreventsinthehistoryofMBPreviewofsomeconceptsandprocessesofMolecularBiologyTranslationProcessofgeneratingaproteinorpolypeptidefromanmRNAmoleculeisknownastranslation.Protein:apolymerorchainofaminoacids,whosesequenceisdeterminedbythemRNAtemplate3nulceotidescodefor20naturallyoccurringaminoacids43=64;thusseveraltrinucleotidesequences(codons)correspondtoasingleaminoacid.Thereisnonucleotidebetweencodons,andafewcodonsrepresentstartandstop.4

RibosomesRibosomes;Factoryforproteinsynthesis;arecomposedofribosomalRNAandribosomalproteins(knownasaRibonucleoproteinorRNP).TheytranslatemessengerRNA(mRNA)tobuildpolypeptidechainsusingaminoacidsdeliveredbytransferRNA(tRNA).5RibosomesEukaryoticribosomes

arelarger.

Theyconsistoftwosubunits;a60SsubunitholdsthreerRNAs(5S,5.8S,28S)andabout40proteins,anda40Ssubunitcontainsan18SrRNAandabout30proteins,whichcometogethertoforman80Sparticlecomparedwithprokaryotic70Sribosome.6

MostmRNAaretranslatedbymorethanoneribosomeatatime;theresult,astructureinwhichmanyribosomestranslateanmRNAintandem,iscalledapolysomes.Polysomes7TheProteinProteins

arethebasicbuildingmaterialsofacell,madebycellitself;thefinalproductofmostgenes.Proteins

arechainlikepolymersofafewormanythousandsofaminoacids.Aminoacidsarerepresentedbycodons,whichare3-nucleotideRNAsequences.Aminoacidsjoinedtogetherbypeptidebonds(polypeptide).Proteinscanbecomposedofoneormorepolypeptidechains.Proteinshavemanyfunctions:providestructurethathelpcellsintegrityandshape(e.g.collageninbone);serveasenzymesandhormones;bindandcarrysubstanceandcontrolactivitiesofgenes….8Fourlevelsofaprotein'sstructure:

Primarystructure:

Formedbyjoiningtheaminoacidsequenceintoapolypeptide.Secondarystructure:

Differentconformationthatcanbetakenbythepolypeptide:alphahelixandstrandsofbetasheet.Tertiarystructure:

Resultfromfoldingthesecondarystructurecomponentsofthepolypeptideintothree-dimensionalconfiguration.Quaternarystructure:

complexofseveralproteinmoleculesorpolypeptidechains,usuallycalledproteinsubunits,whichfunctionaspartofthelargerassemblyorproteincomplex.

9

ProteinStructureBiologicalfunctionofproteinsEnzymecatalysis:DNApolymerases,lactatedehydrogenase,trypsinTransport:hemoglobin,membranetransporters,serumalbuminStorage:ovalbumin,egg-whiteprotein,ferritinMotion:myosin,actin,tubulin,flagellarproteinsStructuralandmechanicalsupport:collagen,elastin,keratin,viralcoatproteinsDefense:antibodies,complementfactors,bloodclottingfactors,proteaseinhibitorsSignaltransduction:receptors,ionchannels,rhodopsin,Gproteins,signallingcascadeproteinsControlofgrowth,differentiationandmetabolism:repressorproteins,growthfactors,cytokines,bonemorphogenicproteins,peptidehormones,celladhesionproteinsToxins:snakevenoms,choleratoxin11TypesofcontrolinEukaryotes

Transcriptional,

regulatetranscription,preventmRNAfrombeingsynthesized.Posttranscriptional,

controlmRNAafterithasbeenproduced.Translational,

preventtranslation;involveproteinfactorsneededfortranslation.Posttranslational,

aftertheproteinhasbeenproduced:modifyproteinstoregulateitshalf-life,localization,etc.MutationMutation

includesbothgrossalterationofchromosomeandmoresubtlealterationtospecificgenesequence.Grosschromosomalaberrationsinclude:largedeletions;additionandtranslocation(reciprocalandnonreciprocal).Mutation

inagene'sDNAsequencecanaltertheaminoacidsequenceoftheproteinencodedbythegene.Pointmutationsaretheresultofthesubstitutionofasinglebase.Frame-shiftmutationsoccurwhenthereadingframeofthegeneisshiftedbyadditionordeletionofoneormorebases.13Mutation

Mutationscanhaveharmful,beneficial,neutral,oruncertaineffectsonhealthandmaybeinheritedas

autosomaldominant,autosomalrecessive,

orX-linkedtraits.Mutationsthatcauseseriousdisabilityearlyinlifeareusuallyrarebecauseoftheiradverseeffectonlifeexpectancyandreproduction.14

CommonToolsinMolecularBiology

NucleicacidfractionationPolymerasechainreactionProbes,HybridizationVector,MolecularcloningNucleicacidenzymesMicroarrayDNAsequencingElectrophoreticseparationofnucleicacidDetectionofgenes:

*DNA:Southernblotting;inSituhybridization;FISHTechnique

*RNA:Northernblotting

*Protein:Westernblotting,immunohistochemistry16MolecularBiology:UsesTheMostRecentAppliedTechnologiesGeneticengineeringinagricultureApplicationinresearchHumangenomeprojectDNAfinger-printinginthesocialandforensicscience.Preandpostnataldiagnosisofinheriteddiseases.Genetherapy.DrugDesignanddrugproduction.ModelBiologicalSystemsFundamentalproblemsaresolvedinthesimplestandmostaccessiblesysteminwhichtheproblemcanbeaddressed.Theseorganismsarecalledmodelorganisms.Virus病毒Bacteria细菌Bacteriophage噬菌体Yeasts酵母Animalcellsandembryos动物细胞和胚Plantcells植物细胞AnimalcellsandembryosThenematode（线虫）CaenorhabditiselegansThefruitfly（果蝇）DrosophilamelanogasterSilkwormThehousemouseMusmusculusMammalianCelllinesEmbryonicstemcellsFeaturesofModelSystemsTheavailabilityofpowerfultoolsoftraditionalandmoleculargenetics.Thestudyofeachmodelsystemattractedacriticalmassofinvestigators.(Ideas,methods,toolsandstrainscouldbeshared)ItdependsonwhatquestionisbeingaskedWhenstudyingfundamentalissuesofmolecularbiology,simplerunicellularorganismsorvirusesareconvenient.Fordevelopmentalquestions,morecomplicatedorganismsshouldbeused.FeaturesofIdealModelSystemsShortergenerationtimeSmalleramountofgeneticmaterialsurvivesandbreedswellinthelabmanyaspectsofitsphenotype(appearance)ThescientificprocessobservationhypothesispredictionexperimentsupportrefuteNewhypothesisRapidprogressinmolecularbiologyRapidprogressinmolecularbiologyhasgeneratedliterallythousandsofvolumesofdetailedinformationaboutthestructureandfunctionofcellularcomponents.Organizingthosedetailsinacomprehensivewayrepresentsachallengeforboththebeginningstudentandtheaccomplishedprofessionalscientist.Inordertodevelopaworkingknowledgeofthediscipline,detailsaboutmolecularstructureandfunctionrequireattention,andgeneralizationsneedtobemade.Puttingthedetailsofmolecularbiologyinperspective“Reductionist”approachbelievethewhole(organism)canonlybefullyunderstoodwhenitisdissectedandanalyzed.Eventually,thelowestcommondenominators,suchasthenatureofthebondingbetweenDNAandproteins,arerevealedandgeneraltheoriesareconstructed.Puttingthedetailsofmolecularbiologyinperspective“Holistic(整体)”approachemphasizestheintegrationofvariousbiologicalphenomenaintohigherordersystems.Insomecases,thosesystemsarerepresentedbyindividualtypesoforganisms,whileinothercasesseveralorganismsareintegratedintoevenhigherordersoforganization,suchasthedisciplinesofanimalorplantecology.PuttingthedetailsofmolecularbiologyinperspectiveIndividualmoleculesare,ofcourse,thebasisofalllivingactivities.Nevertheless,inordertofullycomprehendthefunctionandsignificanceofanysinglemolecule,anexcursionbeyondthetesttubeandperhapsevenoutofthelaboratoryandontobiologicalfieldstationswilleventuallybenecessary.RewardsfromStudying

MolecularBiologyFirst,theuseofthe“layeringapproach”toconstructingaknowledgebase,providesalearningtoolthat,oncemastered,canbeappliedtootherdisciplines,rangingfrompoetrytophysics.Second,studyingmolecularbiologyprovidesanexcellentopportunityforenhancingone’sanalyticalthoughtprocesses(so-called“criticalthinkingskills”).Fromtimetotime,experimentaldataareencountered.Learninghowtointerpretitusuallyinvolvesanalyzingentriesintablesorgraphs,andtherebyimprovesproblem-solvingskills.RewardsfromStudying

MolecularBiologyThird,bylearningtheconceptsanddetailsofmolecularbiology,thebeginningbiologystudentisprovidedagatewaytovirtuallyallotherdisciplinesinbiology,rangingfromcellbiologytogeneticstopopulationbiology.Finally,shouldyou,thebeginningstudent,developaninterestinmolecularbiology,youmightconsiderchoosingacareerinafieldrelatedtothisdiscipline.MajorAspectsofChapter1ConceptofMolecularBiologyGoalsofMolecularBiologyMajoreventsinthehistoryofMBPreviewofMolecularBiologyModelBiologicalSystemsLabMethodsforMolecularBiologyScientificprocessRewardsfromstudyingMBImportantconceptsandfeaturesyouarerequiredtounderstandgenomeFunctionofcellsProkaryoticandEukaryoticcellsEukaryoticDNAProkaryoticDNA4phasesofEukaryoticCellCycleCentralDogmaChromosomehumancellChromosomegenelocusfeaturesofStructureofNucleicAcidhydrogenbondsbetweenbasesG+CcontentandmeltingtemperatureChemicalandstructuralDifferencebetweenDNAandRNAchromatinnucleosomesformsofDNAenzymesinvolvedinDNAReplicationcharacteristicsofMitochondrialDNAlevelsofGeneexpressionwhyandhowtostudyGeneexpressiontranscriptionDifferencebetweenDNAReplicationandtranscriptionGeneticcodesandcodonsStopcodonsDifferenttypesofRNAandfunctionsOpenReadingFrame(ORF)PromoterregionsmRNAuntranslatedregionsCodingandnon-codingRNAexonsandintronssplicingtranslationandribosomespolysomesFourlevelsofaprotein'sstructureTypesofcontrolinEukaryotesMutationCommonToolsinMolecularBiologyMajorapplicationsofMolecularBiologyModelBiologicalSystemsandtheirfeaturesTheendofchapter1Chapter2

TheMacromoleculesoftheCellusethesefourmajorclassesofbiologicalmolecules.ObjectivesThenatureofthecomponentsofthemacromolecules(大分子）ofthecell,andthechemicallinkagesbywhichtheyarejoinedtoformbiopolymers(生物多聚体)Therolethatnon-covalent(非共价的)interactionsplayindeterminingthethree-dimensionalstructureofmacromolecules.MajorlabmethodsforisolationandcharacterizationofproteinandnucleicacidsSmallMoleculesvsMacromoleculesSmallmolecules：molecularweightsusuallydonotexceedseveralhundred.InorganicionsOrganiccompoundsMacromolecules:massivepolymers,molecularweightsovertenthousandProteinsNucleicacidsPolysaccharides(多糖)LipidsMonomers,PolymersandMacromoleculesBiologicalmacromoleculesareformedbylinkingtogetherasetofbuildingblocks(monomers，单体)intolongchains(apolymer).Amassivepolymermakesamacromolecule.CondensationReactionThesemonomersarelinkedtogetherbyaprocesscalleddehydration（脱水）synthesis(alsocalledacondensationreaction)inwhichacovalentbondisformedbetweenthetwomonomerswhileawatermoleculeisalsoformedfromtheOHgroups.Thisreactioniscatalyzedbyenzymes.Thissametypeofcondensationreactioncanoccurtoformdifferentmacromolecules,includingproteins,

nucleicacids,polysacchridesandlipids.30MostCommonMonomersinCellsMoleculeNo.PresentNamesofMoleculesRoleincellAminoacid20Ala(A)Leu(L)Arg(R)Lys(K)Asp(N)Met(M)Asp(D)Phe(F)Cys(C)Pro(P)Gln(Q)Ser(S)Glu(E)Thr(T)Gly(G)Trp(W)His(H)Tyr(Y) Ile(I) Val(V)Monomersofproteinsnucleotides5Adenine Thymine CytosineUracil GuanineMonomersfornucleicacidsSugars2RiboseComponentofnucleicacidsGlucoseComponentofpolysaccharidesEnergymetabolismLipids3Choline胆碱ComponentsofphospholipidsGlycerolPalmitate棕榈酸ProteinsProteinsareLinearChainsofLinkedAminoAcidsException:prolineonlyhasaniminogroupACommonThreadbutaUniqueIdentityAminoacids>60kindsinacell,butonly20involvedinproteinsynthesisThe20essentialaminoacidscanbecategorizedintothreegroupsNon-polar(hydrophobic)（疏水）Polaruncharged(hydrophilic)（亲水）Polarcharged(hydrophilic)FormsaltbridgesContaingroupsthatformhydrogenbondswithwaterPolarunchargedCysteineCysteine(Cys,C，半胱氨酸)hasathiol

(硫醇)group(-SH)，whichisoftenoxidizes（氧化）tocystine（光氨酸）.

DisulfidebondAminoacids-aromatic(芳香族，3)AccountsformostofUVabsorbanceof

proteinsat280nmChirality手性

-carbonischiral(asymmetric不对称的)exceptinglycine(甘氨酸，RisH)ThetwoasymmetricformsarereferredtoasDandLDcomesfromdextrorotatory(右旋，rightturning)Lcomesfromlevorotatory(左旋，leftturning)AllbiologicallyactiveaminoacidsareofLform.PeptidebondPolypeptidesarebuiltthroughaseriesofdehydration(condensation)reactionsTheOHandHgroupsareremovedfromthecarboxylgroupofoneaminoacidandtheaminogroupofthenextaminoacidTheremovalofwaterformsacovalentpeptidebondPeptidebondsPolypeptidescontainNtermini

(aminoterminus)andCtermini(carboxylterminus),usuallyrangingfrom100-1500aa.PeptidebondsN-terminusandC-terminusNterminusCterminusSomeoftheDiverseFunctionsofProteinsPrimaryStructureAminoacidsequenceofaproteinWrittenfromaminoterminustocarboxylterminusCodedforbynucleotidesequencefromthemRNA,thereforerepresentsthecommandsoftheDNAsequenceSequencedeterminessecondary,tertiaryandquaternarystructures,aswellasprotein-proteinandprotein-nucleicacidrecognitionsAsinglesubstitutionmayresultinaproteinthatisnotfoldedproperly(hemoglobin)SecondarystructureFoldingintoahelix,bsheetorrandomcoilInvolveslocalinteractionsbetweenaminoacidsInteractionsleadtotheformationoftheahelixorbsheet己糖激酶ahelixHelixisderivedfromrepeatingpolymersandresultsin3.6aminoacidsperturn,bringingevery4thaminoacidinproximityL

(leu),M(met),andE(glu)arestronghelixformersG(gly)andP(pro)arehelixbreakersandareinvolvedinbendsandturnsinhelicesThebsheetMaximizedbyhydrogenbonding,butbetweentwopolypeptidesortwodifferentsegmentsofonepolypeptideI(ile),V(val),andF(phe)arestrongsheetformersIfthetwostrandslinkedarealignedwithbothaminoandbothcarbonylgroupsrunninginthesamedirection,thenthisisaparallelsheetIfthetwostrandsruninoppositedirections,thisisananti-parallelsheetMotifsMotifs:commonlyoccurringsecondarystructures

b-a-bmotifHairpinturnmotifHelix-turn-helixmotifTertiarystructuredependsmoreontheRgroupsthantheaminoorcarboxylgroupsHydrophobicdomainstendtoassociatewithoneanotherandareoftenfoundintheinnersectionsoftheproteinStabilizationoftertiarystructuresNoncovalentbondsHydrogenbondsbetweenappropriateRgroupsElectrostaticinteractionsbetweenchargedRgroupsHydrophobicinteractionsbetweennonpolarRgroupsCovalentbondsDisulfidebondbetweentwocysteineresiduesDisulfidebondsareimportantforstabilizingbothtertiaryandquaternarystructuresProteindomainMostglobular(球状)proteinsconsistsofseveraldomains(结构域)Adomainisadiscrete,locallyfoldedunitoftertiarystructure50-350residuesEachdomainhasaspecificfunctionwithintheprotein,suchasmetalbindingdomainofenzymesSmallglobularproteinstendtohaveasingledomainLargeglobularproteinshavemultipledomainsQuaternaryStructureLevelofproteinorganizationrelatedtosubunitinteractionsandassembliesProteinsstructuresLevelofstructureBasisofStructureBondsinvolvedPrimaryAminoacidsequenceCovalentbondsSecondaryFoldingintoahelix,bsheetorrandomcoilHydrogenbondsTertiary3DfoldingofasinglepolypeptideHydrogenanddisulfidebonds,electrostaticandhydrophobicinteractionsQuaternaryAssociationof2ormorefoldedsubunitsSameastertiaryNucleicAcidsNucleicAcidsLinearpolymersofnucleotidesStore,carry,andaidinthetransmissionofgeneticinformationDifferintypeofsugarusedandlengthofpolymersDeoxyribonucleicacid(DNA)Ribonucleicacid(RNA)Sugarineachcaseisthepentose(五元糖)BackgroundIn1869,FriedrichMeischerisolatedDNAfromfishspermandthepusofopenwounds.Sinceitcamefromnuclei,Meischernamedthisnewchemical,nuclein(核素）.Subsequentlythenamewaschangedtonucleicacidandlastlytodeoxyribonucleicacid(DNA).In1914,RobertFeulgen（福尔根）discoveredthatfuchsin（品红）dyestainedDNA.DNAwasthenfoundinthenucleusofalleukaryoticcells.

BackgroundDuringthe1920s,biochemistP.A.LeveneanalyzedthecomponentsoftheDNAmolecule,whichcontainedfournitrogenousbases:cytosine,thymine,adenine,andguanine;deoxyribosesugar;andaphosphategroup.Heconcludedthatthebasicunit(nucleotide)wascomposedofabaseattachedtoasugarandthatthephosphatealsoattachedtothesugar.Unfortunately,heincorrectlyconcludedthattheproportionsofbaseswereequalandthattherewasatetranucleotide(四核苷酸）thatwastherepeatingstructureofthemolecule.ComponentsofNucleicacids EachnucleotidehasthethreefollowingcomponentsAcyclicfive-carbonsugar:riboseinRNA，ordeoxyribose(脱氧核糖)inDNA.Apurine(嘌呤)orpyrimidine（嘧啶）baseattachedto1’-carbonatomofsugarbyN-glycosylic(糖基)bond.Aphosphateattachedtothe5’carbonofthesugarbyaphosphoester(磷酯)linkage.ComponentsofNucleicacids:PhosphateandpentosePurinesandpyrimidinescanformchemicallinkageswithpentose(5-carbon)sugars.Thecarbonatomsonthesugarsaredesignated1',2',3',4'and5'.Itisthe1'carbonofthesugarthatbecomesbondedtothenitrogenatomatpositionN1ofa

pyrimidineorN9ofapurine.DNAprecursorscontainthepentosedeoxyribose.RNAprecursorscontainthepentoseribose(whichcontainsanadditionalhydroxylgroup(羟基)atthe2'position)NucleotidesAretheMonomersThatCreatePolymersofDNAandRNABasesareinsideSugarandPareoutsideOfthehelixhydrogenbondinginNucleicAcidsREQUIREDFORSPECIFICITYOFBASEPAIRINGRecognitionofcomponentmoleculesdependsonfeaturesofpurinesandpyrimidinesCarbonylgroupsandnitrogenarecapableofhydrogenbondingHydrogenbondsformbetweenA:TorA:UorbetweenG:CNOTVERYIMPORTANTINDNASTABILIZATIONHYDROPHOBICFORCESARETHEMOSTIMPORTANTDNAconformationsDNAcanhaveseveralconformations.ThemostcommononeiscalledB-DNA.B-DNAisaright-handeddoublehelixwithawideandnarrowgroove(槽).Thebasesareperpendicular(垂直)tothehelixaxis.B-DNADNAconformationsDNAcanalsobefoundintheAforminwhichthemajorgrooveisverydeepandtheminorgrooveisquiteshallow.AformDNAconformationsAveryunusualformofDNAistheleft-handedZ-DNA.Z-DNAformsexcellentcrystals.Z-DNARNAconformationRNAcanformdoublestrandedduplexes.TheseduplexesareintheAconformationbecausethe2'OHprecludestheBconformation.Morecommonly,RNAissinglestrandedandcanformcomplexandunusualshapes.A-RNACarbohydratesCarbohydratesMonosaccharides-simplesugarswithmultipleOHgroups.Basedonnumberofcarbons(3,4,5,6),amonosaccharideisatriose,tetrose,pentoseorhexose.Disaccharides-2monosaccharidescovalentlylinked.Oligosaccharides-afewmonosaccharidescovalentlylinked.Polysaccharides-polymersconsistingofchainsofmonosaccharideordisaccharideunits. Structure:

MonosaccharidesAldoses(e.g.,glucose)haveanaldehydegroupatoneend.Ketoses

(e.g.,fructose)havea

keto

group,usuallyatC2.

DandLsugarsForsugarswithmorethanonechiralcenter,DorLreferstotheasymmetricCfarthestfromthealdehydeorketogroup.MostnaturallyoccurringsugarsareDisomers.DandLsugarsaremirrorimagesofoneanother.GlycosidicBondsThehydroxylgroupofonesugarandthehydroxylgroupofanothersugarorsomeothercompoundcanjointogether,splittingoutwatertoformaglycosidicbond: R-OH+HO-R'

R-O-R'+H2OE.g.,methanolreactswithanOHonglucosetoformmethylglucoside.Cellobiose,aproductofcellulosebreakdown,istheotherwiseequivalentbanomer(OonC1pointsup).Theb(14)glycosidiclinkageisrepresentedasazigzag,butoneglucoseisactuallyflippedoverrelativetotheother.Disaccharides:Maltose,acleavageproductofstarch,isadisaccharidewithana(14)glycosidiclinkbetweentheC1OH&C4OHof2glucoses.Itistheaanomer,becausetheOonC1pointsdown.DisaccharidesOthercommondisaccharidesinclude:Sucrose,commontablesugar,hasaglycosidicbondlinkingtheanomerichydroxylsofglucose&fructose.BecausetheconfigurationattheanomericCofglucoseisa(Opointsdownfromring),thelinkageisa(12).Thefullnameofsucroseisa-D-glucopyranosyl-(12)-b-D-fructopyranose.)Lactose,milksugar,iscomposedofgalactose&glucose,withb(14)linkagefromtheanomericOHofgalactose.Itsfullnameisb-D-galactopyranosyl-(14)-a-D-glucopyranosePolysaccharides多糖Theyareverycomplexmoleculesbecausesometimescovalentbonds共价键occurbetweenmanypartsofcarbonatoms,allowingonesugarunittobejoinedtomorethantwoothersugars,whichresultsintheformationofhighlybranchedmacromolecules.Polysaccharidesplayvariousroles,fromenergystorage(starch,glycogen)tostructure(cellulose).GlucoseStorageinPlantsPlantsstoreglucoseasamyloseoramylopectin,glucosepolymerscollectivelycalledstarch.Glucosestorageinpolymericformminimizesosmoticeffects.Amyloseisaglucosepolymerwitha(14)linkages.TheendofthepolysaccharidewithananomericC1notinvolvedinaglycosidicbondiscalledthereducingend.Amyloseadoptsahelicalconformation.Amylopectinisaglucosepolymerwithmainlya(14)linkages,butitalsohasbranchesformedbya(16)linkages.Branchesaregenerallylongerthanshownabove.Thebranchesproduceacompactstructure&providemultiplechainendsatwhichenzymaticcleavagecanoccur.Glycogen,theglucosestoragepolymerinanimals,issimilarinstructuretoamylopectin.Butglycogenhasmorea(16)branches.Thehighlybranchedstructurepermitsrapidreleaseofglucosefromglycogenstores,e.g.,inmuscleduringexercise.Theabilitytorapidlymobilizeglucoseismoreessentialtoanimalsthantoplants.Cellulose,amajorconstituentofplantcellwalls,consistsoflonglinearchainsofglucosewithb(14)linkages.Theroleofcelluloseistoimpartstrengthandrigiditytoplantcellwalls.LipidsLipidsLipidsarenon-polar(hydrophobic)compounds,solubleinorganicsolvents.Mostmembranelipidsarehipathic,havinganon-polarendandapolarend.Fattyacids,thesimplestlipids,consistofahydrocarbonchainwithacarboxylicacidatoneend.an16-Cfattyacid: CH3(CH2)14-COO- Non-polarpolarGlycerophospholipidsGlycerophospholipids(phosphoglycerides),arecommonconstituentsofcellularmembranes.Theyhaveaglycerolbackbone.HydroxylsatC1&C2areesterifiedtofattyacids.GlycerophospholipidEachglycerophospholipidincludesapolarregion:glycerol,carbonyloffattyacids,Pi,&polarheadgroup(X)2non-polarhydrocarbontailsoffattyacids(R1,R2).Phosphatidylcholine,withcholineaspolarheadgroup,isanexleofaglycerophospholipid.Itisacommonmembrane