一到二章細(xì)胞介紹

IntroductiontoCellBiologyDr.AnWeiDepartmentofCellBiologyCapitalMedicalUniversityIn1665,RobertHookewrote:“Itookagoodclearpieceofcork,andwithpenknifeofsharpen’daskeenasRazor,Icutapieceofitoff,andthenex-amineditwithmicroscope,methoughtIcouldperceiveittoappearalittleporous…muchlikeab.”CellainLatinmeans“l(fā)ittlebox”,Infact,theseso-calledlittleboxisactuallycellwallofthediedcell。DiscoveryofcellsAntonvanLeeuwenhoekanothergreatcellbiologistTheDutchnaturalistandmicroscopistAntonvanLeeuwenhoek(1632-1723),usingsimplemicroscopesofhisownmaking,discoveredbacteria,protozoa,spermatozoa,rotifers,HydraandVolvox,andalsoparthenogenesisinaphids.

FormulationoftheCellTheory

Allorganismsarecomposedofoneormorecells.Cellsarethesmallestlivingthings.Cellsareformedourofspontaneousprocesslikecrystal.Thecelltheory(proposedindependentlyin1838and1839)isacornerstoneofbiology.SchleidenSchwannRudolphCarlVirchow

ThecorrectinterpretationofcellformationbydivisionwasfinallypromotedbyothersandformallyenunciatedinRudolphVirchow’spowerfuldictum,Omniscellulaecellula…:“Allcellsonlyarisefrompre-existingcells”.Overview:TheImportanceofCellsAllorganismsaremadeofcells.Thecellisthesimplestcollectionofmatter

thatcanlive.Allcellscomefromdivisionofpre-existingcells10μm1865

GregorMendelphenotypicbasisofinheritance1868

FriedrichMeischerdiscovers"nuclein"-inpus&fishsperm1887

AugustWeismanndescribesreductiondivisionofchromosomes1903

WalterSuttondescribesmeiosis&spermatogenesisininsects

"ChromosomalTheoryofInheritance"1909

ThomasHuntMorganDrosophilia,chromosmallinkage&crossingover1911

AlfredStuartevantmappingofgenesonchromsomes1924

RobertFuelgencytochemicalstaining&identificationofDNA1928

FredGriffithusedpneumococcus&describedgenetransformation1933

TedPainteridentifiespolytenechromosomes

1930'sGeorgeBeadle&EdTatum"onegene-oneenzyme"

1940's

LinusPauling

peaceidentifiesalphahelixstructureofproteins

1940'sMauriceWilkins&

RosyFranklin

X-raydiffraction-structureofDNA1944

OswaldAvery,

MaclynMacLeod,&ColinMcCartychemicallysuggestthat"DNAisgeneticmaterial"1950

ErwinChargaff"Chargaff'sRule"-DNAbasecomplimentarityA:TG:C1950'sFredSanger

tRNAsequences1stprotein-insulin1952

AlfredHershey&

MarthaChase

32PviralDNAreplication=genesareDNA1953

JamesWatson&

FrancisCrickidentifymodelstructureofDNA1956

ArthurKornbergdescribesactionofDNApolymerase

1950'sPeterMitchellChemiosmosis-howcellsmakeATP

1958

MattMeselson&FrankStahlsemiconservativereplicationofDNA1960PaulDoty&JayMarmur

Tm-hyperchromicityDNA-DNAhybridization1961

Holley,Khorana,&Nirenberg&HenirichMattaei

identifiesGeneticCode

1963

JeromeVinograd

identifiessuper-coiledstructureofDNA1968StanleyCohendiscoversplasmids&antibioticresistance1969

Edmonds&Caramelaiidentifiespoly-A-polymeraseABrief&pleteHistoryofCellandMolecularBiology

1970HerbertBoyerdiscoversrestrictionendonuclease1971GunterBlobelsignalhypothesis1972PaulBergRecombinantDNA's-splicesSV40&Ecoli1975WalterGilbert,allanMaxam,FredSangerdevelopDNAsequencestechniques1975CesarMilstein,Geo.Kohler,&NilesJemedevelopmonoclonalantibodies1976RobertSwanson&HerbBoyercreateGENENTECHbiopharmaceuticalCo.1977

RichardRoberts&

PhilipSharpidentifiessplitgenes(introns&exons)1978Genentech,Inc.producesHumulin1strecombinantDNAdrug1981

SidneyAltman&TomCechidentifiesribozymes

1985KaryMulliscreatesPCR-PolymeraseChainReaction1989HGPProjectprojecttosequenceentirehumangenome1990FrenchAnderson1stuseofRecombinantDNAdrug(ADA)1992HarryNollerpeptidyltransferaseisaribozyme1992

EdmundFischer&

EdwinKrebsidentifyproteinphosphorylation1993

KerryMulliscreatesPCRreaction1994CalgeneFlavrSavrtomato1sttransgenicfood1996IanWilmutmammaliancloning&Dolly1997

PaulBoyer&JohnWalkerdescribesATPsynthasemechanism1998JamesThompson&JohnGearhartplueripotent(stem)cellscultured1999CraigVentercompletegenesequenceofDrosophilaidentified2000CraigVenterHumanGenomesequenceannouncedABrief&pleteHistoryofCellandMolecularBiology(cont’s)Twocelltypes-TheThreeDomainSystemProkaryotes

AllcellshaveseveralbasicfeaturesincommonTheyareboundedbyaplasmamembraneTheycontainasemifluidsubstancecalledthecytosolTheycontainchromosomesTheyallhaveribosomes

TwotypesofcellsmakeupeveryorganismProkaryoticcellEukaryoticcellProkaryoticcellsDONOTcontainanucleusenclosingDNADO

containtheirDNAlocatedinaregioncalledthenucleoid(nucleus-likestructure)(b)AthinsectionthroughthebacteriumBacilluscoagulans(TEM)Pili:attachmentstructuresonthesurfaceofsomeprokaryotesNucleoid:regionwherethecell’sDNAislocated(notenclosedbyamembrane)Ribosomes:organellesthatsynthesizeproteinsPlasmamembrane:membraneenclosingthecytoplasmCellwall:rigidstructureoutsidetheplasmamembraneCapsule:jelly-likeoutercoatingofmanyprokaryotesFlagella:localmotionorganellesofsomebacteria(a)Atypicalrod-shapedbacterium0.5μmBacterial

chromosomeEukaryoticcellsContainatruenucleus,boundedbyamembranousnuclearenvelopeAremorecomplicatedingeneprocessingthanprokaryoticcells-

Arerichininternalmembranesystemthatcompartmentalizetheir

functionsRoughERSmoothERCentrosomeCYTOSKELETONMicrovilliLysosomeGolgiapparatusRibosomesNucleolusChromatinNUCLEUSFlageliumENDOPLASMICRETICULUM(ER)MitochondrionNuclearenvelopePlasmamembranecytoplasm-Containingavarietyofmembrane-boundedorganelles.Prokaryotic

vs.

EukaryoticcellsSizeandcomplexity:differsinsizeandgenesystemBasicstructure:nucleus,plasmamembrane,cytosol,

chromosomes,ribosomes,…

Difference:

asindicatedbytheirnames:ProkaryoticEukaryotic

nucleoidnucleus(nomembrane)

(containingmembranousnuclearenvelope)ChromosomeslocationPossessonlyribosomeSeveralorganelles

1-10mm

10-100mmCytoplasmSizeUsvs.ThemChromosomeslocation10-100mm1-10mm10-100

mmSizeOrganizationMetabolismOrganellesEukaryotes

&ProkaryotesSurfaceareaincreaseswhiletotalvolumeremainsconstant511Totalsurfacearea(height

width

numberofsides

numberofboxes)Totalvolume(height

width

length

numberofboxes)Surface-to-volumeratio(surfacearea

volume)6161501251.27501256ThelogisticsofcarryingoutcellularmetabolismsetslimitsonthesizeofcellsAsmallercellHasahighersurfacetovolumeratio,whichfacilitatestheexchangeofmaterialsintoandoutofthecellOverviewofmajorcomponentsofeukaryoticcellarchitecture(5x5x6)(6x125)AnIdealizedAnimalCellCellularAnatomyTheplasmamembraneFunctionsasaselectivebarrierFigure6.8A,BCarbohydratesidechainOutsideofcellInsideofcellHydrophilicregionHydrophobicregionHydrophilicregion(b)StructureoftheplasmamembranePhospholipidProteinsTEMofaplasmamembrane.Theplasmamembrane,hereinaredbloodcell,appearsasapairofdarkbandsseparatedbyalightband.(a)0.1μm-AllowssufficientnutrientsandwastesaswelltopassthroughRoughERSmoothERCentrosomeCYTOSKELETONMicrofilamentsMicrotubulesMicrovilliPeroxisomeLysosomeGolgiapparatusRibosomesInanimalcellsbutnotplantcells:LysosomesCentriolesFlagella(insomeplantsperm)NucleolusChromatinNUCLEUSFlageliumIntermediatefilamentsEndoplasmicreticulum(ER)MitochondrionNuclearenvelopePlasmamembraneInternalmembranesystemHaveextensively-andelaborately-arrangedinternalmembranes,whichformorganellesSuchas:endoplasmicreticulum(ER),

Golgiapparatus,lysosome,peroxisome.

regulatesproteintrafficandperformsmetabolicfunctionsinthecell

Theendomembrane(orinternalmembrane)systemIncludesmanydifferentstructuresTheendomembranesystemTheendoplasmicreticulum(ER)AccountsformorethanhalfthetotalmembraneinmanyeukaryoticcellsEndoplasmicreticulum(ER)

endoplasmic-“withinthecytoplasm”reticulum-“l(fā)ittlenet”

*cisternae(membranoustubules&

sacs;reservoirforaliquid)

TheERmembraneIscontinuouswiththenuclearenvelopeSmoothERRoughERERlumenCisternaeRibosomesTransportvesicleSmoothERTransitionalERRoughER200μmNuclearenvelopeFigure6.12TherearetwodistinctregionsofERSmoothER,whichlacksribosomesRoughER,whichcontainsribosomesSmoothER:lacksribosomesRoughER:containingribosomes

(cytoplasmicsurface)SmoothER:RoughER:SmoothER:

functionsindiversemetabolicprocessesinvariouscelltypes,includingsynthesisoflipids,metabolismofcarbohydrates,

storeCa2+

anddetoxification

ofdrugsandpoisons.

*steroids:sexhormones(testesandovariesarerichinsmoothER)*Livercells

(detoxificationex.sedativephenobarbitalhowever,increasetoleurance)*Musclecell:sERstoreCa2+

Ca2+pump(cytosolERlumen)TransportvesiclesSmoothERRoughERERlumenCisternaeRibosomesTransportvesicleTransitionalERNuclearenvelopeRoughER:

*synthesizesecretoryproteins.ex.Pancreas:insulin~mostsecretoryproteinsareglycoproteins(thecarbohydrateisattachedtotheproteinintheER)

*membranefactory:

membraneproductionRibosomesAreparticlesmadeofribosomalRNAandproteinCarryoutproteinsynthesis

freeribosomes:incytosol

boundribosomes:attachedtooutsideoftheERornuclearenvelopRibosomes:ProteinFactoriesintheCellERRibosomesCytosolFreeribosomesBoundribosomesLargesubunitSmallsubunitTEMshowingERandribosomesDiagramofaribosome0.5μmEndoplasmicreticulum(ER)StructurallyidenticalandcanalternatebetweenthetworolesERandhumandiseasesAATdeficiencyoftenresultsinabnormalfoldingofthemutatedproteinwithabnormalaccumulationintheendoplasmicreticulumofhepatocyteswhereproteinsaresynthesized.Intra-hepatocyteretentionoftheabnormalAATproteinimpairssecretionandresultsinreducedlevelsofAATintheblood.ALPHA-1ANTITRYPSINDEFICIENCY

TheGolgiapparatusReceivesmanyofthetransportvesiclesproducedintheroughERAsacenterofmanufacturing,warehousing,sorting,andshippingConsistsofflattenedmembranoussacscalledcisternaeTheGolgiApparatus:

FunctionsoftheGolgiapparatusincludeModificationoftheproductsoftheroughERManufactureofcertainmacromolecules(ex.pectinandnon-cellulosepolysaccharides)GlycosylationPro-activetoactiveformofproteinGolgiapparatusTEMofGolgiapparatuscisface(“receiving”sideofGolgiapparatus)VesiclesmovefromERtoGolgiVesiclesalsotransportcertainproteinsbacktoERVesiclescoalescetoformnewcisGolgicisternaeCisternalmaturation:Golgicisternaemoveinacis-

to-trans

directionVesiclesformandleaveGolgi,carryingspecificproteinstootherlocationsortotheplasmamem-braneforsecretionVesiclestransportspecificproteinsbackwardtonewerGolgicisternaeCisternaetransface(“shipping”sideofGolgiapparatus)0.10μm165234Golgiapparatus:hasadistinctpolarity“cisternalmaturationmodel”SubstancemovementfromERtoGolgiApparatusPlasmamembraneexpandsbyfusionofvesicles;proteinsaresecretedfromcellTransportvesiclecarriesproteinstoplasma

membraneforsecretionLysosomeavailableforfusionwithanothervesiclefordigestion456NuclearenvelopeisconnectedtoroughER,

whichisalsocontinuouswithsmoothERNucleusRoughERSmoothERcisGolgitransGolgiMembranesandproteinsproducedbytheERflowintheformoftransportvesiclestotheGolgiNuclearenvelopGolgipinchesofftransportVesiclesandothervesicles

thatgiverisetolysosomesandVacuoles132PlasmamembraneFunctionsoftheGolgiapparatusincludeModificationoftheproductsoftheroughERManufactureofcertainmacromolecules(ex.pectinandnon-cellulosepolysaccharides)GlycosylationPro-activetoactiveformofproteinBloodtypearedeterminedbyglycolipidN-乙酰半乳糖胺轉(zhuǎn)移酶半乳糖胺轉(zhuǎn)移酶Mother/FatherOABABOOO,AO,BABAO,AO,AO,A,B,ABA,B,ABBO,BO,A,B,ABO,BA,B,ABABA,BA,B,ABA,B,ABA,B,ABAlysosome

acidic

pH(pH5)IsamembranoussacofhydrolyticenzymesCandigestallkindsofmacromoleculesHydrolyticenzymesandlysosomalmembranearemadebyrERGolgiLysosomes:Lysosomescarryoutintracellularingestion

ofsubstancesviaPhagocytosis(“eating”)

andpicocytosis(“drinking”)digestionproductspassintothecytosolandethenutrientsforthecell.-autophagy:recyclethecell’sownorganicmaterial.ex.Liver.DigestiveCompartmentsLysosomescarryoutintracellularinjectionbyPhagocytosisPincocytosis

(a)Phagocytosis:lysosomedigestingfood1μmLysosomecontainsactivehydrolyticenzymesFoodvacuole

fuseswith

lysosomeHydrolyticenzymesdigestfoodparticlesDigestionFoodvacuolePlasmamembraneLysosomeDigestiveenzymesLysosomeNucleusAutophagy(b)Autophagy:lysosomebreakingdowndamagedorganelleLysosomecontainingtwodamagedorganelles1μmMitochondrionfragmentPeroxisomefragmentLysosomefuseswithvesiclecontainingdamagedorganelleHydrolyticenzymesdigestorganellecomponentsVesiclecontainingdamagedmitochondrionDigestionLysosome*Tay-Sachsdisease:alipid-digestingenzymeismissingorinactivePostero-anterior(PA)chestradiographina58-year-oldmanwithahistoryofoccupationalexposuretoasbestosshowsrightdiaphragmaticpleuralplaquecalcifications,linearcalcificationalongtheleftpericardium,andbilateralpleuralplaquesalongupperribs.Asbestos

Asbestosisanaturallyoccurring,fibroussilicate.

Silicosisandasbestosis-Silica,suchasfoundinmines,andasbestosaremineralswhichconsistofsharpneedles.Theseareendocytosedintocellsliningthelungsandthevesiclesfusedwithlysosomes.But,theenzymesinthelysosomecan'tdigestthemineralmaterials.Worseyet,theneedlelikeshapesoftheinjestedparticlespuncturethefusedvesicles,releasingenzymesintothecellinterior.Tay-SachsDiseaseiscausedbyadefectinoneenzyme(HexosaminidaseA)catalyzingastepinthelysosomalbreakdownofganglioside.Theresultingaccumulationoftheseglycolipids,especiallyinnervecell,hasdevastatingconsequences.Thesymptomsofthisdiseaseareusuallyevidentbeforeageof1.Affectedchildrencommonlyedementedandblindbyage2anddiebeforetheirthirdbirthday.GalNAcGalGluCeramideSiAGangliosideFindingsinretina“cherryredspot”AmericanneurologistBernardSachsBritishophthalmologistWarrenTay

BernardSachs

Tay-Sachsdiseasecurrentlyhasnotreatment,nocure,andisfatalinchildrenDakotaisan9-yearoldfromOlmstedFalls,Ohiothatisbattlingthishereditary,degenerativeneurologicaldisease.DakotaunderwentacordbloodtransplantatDukeMedicalCenterinJanuaryof2006,butthediseasecontinuestoprogress.

Sheisslowlylosinghermentalandphysicalcapabilitiesbecauseherbodyismissingavitalenzymeneededtoclearwastefrombraincells.Oneinevery250peoplecarriesthisfatalgenemutationthatispassedontoachildwhentwocarrierparentspassthegenetotheirbaby.Thecarrierratesincreaseto1in27intheAshkenaziJewish,LouisianaCajun,andFrenchCanadianpopulations.TheIrishAmericanpopulationfinds1inevery50peopletobecarriersoftheTay-Sachsgene.Mitochondrion

Inmammalcells:thesiteswherethecellularrespirationandenergygenerationtakeplaceInplantcells:referredas

Chloroplasts,thesitesofphotosynthesisTheMitochondrionThinkofthemitochondrionasthepowerhouseofthecell.Bothplantandanimalcellscontainmanymitochondria.(Mitochondriaisthepluralofmitochondrion)MitochondriaArefoundinnearlyalleukaryoticcellsMitochondria:ChemicalEnergyConversionMitochondriaareenclosedbytwolayersofmembranesAsmoothoutermembraneAninnermembranefoldedintocristaeMitochondrionIntermembranespaceOutermembraneFreeribosomesinthemitochondrialmatrixMitochondrialDNAInnermembraneCristaeMatrix100μm

Mitochondria&Chloroplasts

mainenergytransformersofcells.notpartoftheendomembranesystem.

containingribosomes,andasmallamountofDNA.

semiautonomousorganelles(growthandreproduce)

Mitochondria:cellularrespiration(generatesATPbyextractingenergyfromsugars,fats,andotherfuelswiththehelpofO2)

Chloroplasts:photosynthesis(onlyinplantsandalgae)

ThechloroplastIsaspecializedmemberofafamilyofcloselyrelatedplantorganellescalledplastids(ex.amyloplast,chromoplast)ContainschlorophyllArefoundinleavesandothergreenorgansofplantsandinalgaeChloroplasts:CaptureofLightEnergyChloroplastChloroplastDNARibosomesStromaInnerandoutermembranesThylakoid1μmGranumChloroplaststructureincludes-Thylakoids,membranoussacs-Stroma,theinternalfluidStructureofmitochondrionFunctionsofmitochondrionMitochondriaandHealthCaloricrestrictionprolongslifespanca.50%-70%inratsTheratsareboth1000daysold,veryoldforrats.Theoneontherightwascalorierestricted.Theoneontheleftisneardeathandshowstypicalsignsofoldagesimilartowhathappensinhumans.ImagecitedfromCliveMcCay1939.Leber遺傳性視神經(jīng)病雙胞胎患病兄弟視乳頭盤血管膨脹、視神經(jīng)萎縮ThestereotypedpresentationofLHONcomprisesrapidlossofcentralvisioninoneeye,usuallydescribedaspainlessblurringwithfadingofcolors(dyschromatopsia),followedbysimilarinvolvementoftheothereye,withadelayvaryingfromdaystomonths,rarelyyears.Peroxisomes

SinglemembraneContainenzymethattransferhydrogenfromvarioussubstratestooxygen,producinghydrogenperoxideasaby-product.ChloroplastPeroxisomeMitochondrion1μmFigure6.19Peroxisomes:Oxidation*Breakfattyaciddowntosmallermolecules

mitochondria*DetoxificationinliverAlsocontainenzymethatconvertstheH2O2towater(proteinsaremadeprimarilyinthecytosol,lipidsaremadeintheER,andwithintheperoxisomeitself)

composedofthreewell-definedfilamentousstructures

-Microfilaments(actin)

-Microtubules(tubulin)

-Intermediatefilamentssmallestindiameterinskeletonsystemlargestindiameterinskeletondiameterin-betweenabovetwoskeletonsCytoskeletonCytoskeletonTherearethreemaintypesoffibersthatmakeupthecytoskeletonTable6.1Microfilaments(ActinFilaments)0.25μmMicrovillusPlasmamembraneMicrofilaments(actinfilaments)IntermediatefilamentsFigure6.26“Cortex”outercytoplasmiclayer

semisolidgel~Arebuiltfrommoleculesoftheproteinactin~beartension(pullingforces)~Incombinationwithotherproteins,theyforma3Dnetworkjustinsidetheplasmamembrane,helpingsupportthecell’sshape.~Ex.foundinmicrovilliMicrofilamentsthatfunctionincellularmotilityContaintheprotein

myosin

inadditionto

actinContractionofthemusclecellresultsfromtheactinandmyosinfilamentsslidingpastonanother,shorteningthecellActinfilamentMyosinfilamentMyosinmotorsinmusclecellcontraction.(a)MusclecellMyosinarmFigure6.27AStructureofmusclecellMusclecontractionDuchennemusculardystrophyAmoeboidmovement(localizedcontraction)InvolvesthecontractionofactinandmyosinfilamentsCortex(outercytoplasm):gelwithactinnetworkInnercytoplasm:solwithactinsubunitsExtendingpseudopodium(b)AmoeboidmovementFigure6.27BPseudopodiaextendandcontractthroughthereversibleassemblyofactinsubunitsintomicrofilamentsandofmicrofilamentsinnetworksthatconvertcytoplasmfromsoltogel.CytoplasmicstreamingNonmovingcytoplasm(gel)ChloroplastStreamingcytoplasm(sol)ParallelactinfilamentsCellwall(b)CytoplasmicstreaminginplantcellsFigure6.27C~Isanotherformofotioncreatedbymicrofilaments~Bothactin-myosininteractionsandsol-geltransformationbroughtbyactinmayinvolvedin.~Commoninlargeplantcells,speedsthedistributionofmaterialswithinthecell.Microtubules

hollowtubes;25nm(13columnsoftubulinmolecules)tubulinmolecules:adimerconsisting

a-,andb-tubulindynamic(200nm~25mminlength)

*compression-resisting1.shapeandsupportthecell2.serveastracksformovingtheorganelles(withmotorprotein)ex.~guidesecretoryvesicles:(Golgiapparatusplasmamembrane)~chromosomemovementsincelldivision

~

constructionofcentrosomes,ciliaandflagellaCentrosomesandcentrioles“microtubule-organizingcenter”(MTOC)~inmanycells,microtubulesgrowoutfromacentrosome

(nearnucleus)9tripletMT*Apairofcentrioles(notessentialfororganizingmicrotubuleassembly;mostplantslackcentrioles)CiliaandflagellaContainspecializedarrangementsofmicrotubulesAreotorappendagesthatprotrudefromsomecellsFlagellabeatingpatternDirectionofswimmingFigure6.23CiliarymotionTheproteindyneinmotorprotein-Isresponsibleforthebendingmovementofciliaandflagella-“ATP”drivingtheconformationalchangeofdynein

MicrotubuledoubletsATPDyneinarmPoweredbyATP,thedyneinarmsofonemicrotubuledoubletgriptheadjacentdoublet,pushitup,release,andthengripagain.Ifthetwomicrotubuledoubletswerenotattached,theywouldsliderelativetoeachother.(a)Figure6.25AOuterdoubletscross-linkingproteinsAnchorageincellATPInaciliumorflagellum,twoadjacentdoubletscannotslidefarbecausetheyarephysicallyrestrainedbyproteins,sotheybend.(OnlytwoofthenineouterdoubletsinFigure6.24bareshownhere.)(b)Figure6.25B132*radialspokesVesicleATPReceptorformotorproteinMotorprotein(ATPpowered)Microtubuleofcytoskeleton(a)Motorproteinsthatattachtoreceptorsonorganellescan“walk”theorganellesalongmicrotubulesor,insomecases,microfilaments.MicrotubuleVesicles0.25μm(b)Vesiclescontainingneurotransmittersmigratetothetipsofnervecellaxonsviathemechanismin(a).InthisSEMofasquidgiantaxon,two

vesiclescanbeseenmovingalongamicrotubule.(Aseparatepartofthe

experimentprovidedtheevidencethattheywereinfactmoving.)Figure6.21A,BCytoskeletalelementsandmotorproteinsworktogetherwithplasmamembranemoleculestoallowwholecellstomovealongfiversoutsidethecell.(changeincelllocation)ThevesiclesthatbudofffromtheERtraveltotheGolgialongtracksbuiltofcytoskeletalelements.(movementsofpartofthecell)

TwoproteinsDyneinandKinesin~responsiblefortransportofsubstancealong microtubulesIntermediatefilaments

8~12nm,specializedforbearingtensionareadiverseclassofcytoskeletalelements(typeI-V)(belongtoafamilyofproteincontaining“keratins”)aremorepermanentfixturesofcellsthanmicrofilamentsandmicrotubules.

Maintenanceofcellshape(reinforcingtheshapeofacell)fixorganellesinplace

FormationofnuclearlaminaIntermediatefilamentsGlialfibrillaryacidicprotein(GFAP)andvimentinarebothmembersoftheclassIIIintermediatefilamentproteinfamilythatwerevisualizedintherathypothalamussectionillustratedabove,whichprominentlyfeaturesthethirdventricle.Intermediatefilament

ThecytoskeletonisanetworkoffibersthatorganizesstructuresandactivitiesinthecellMicrotubule0.25μmMicrofilamentsRolesoftheCytoskeleton:Support,Motility,andRegulationThecytoskeleton~Givesmechanicalsupporttothecell(maintainshape)~providesanchorageformanyorganellesandcytosolicenzymemolecules~Isinvolvedincellmotility

(changesincelllocationormorelimitedmovementsofpartofthecell)whichutilizesmotorproteinsCiliaandflagellashareacommonultrastructure(a)(c)(b)OutermicrotubuledoubletDyneinarmsCentralmicrotubuleOuterdoubletscross-linkingproteinsinsideRadialspokePlasmamembraneMicrotubulesPlasmamembraneBasalbody0.5μm0.1μm0.1μmCrosssectionofbasalbodyTripletFigure6.24A-C~eachhasacoremicrotubulessheathedinanextensionoftheplasmamembrane.“9+2”pattern

(9doublets&2centralmicrotubule)moterproteinstructurallyidenticaltoacentrioleExtracellularcomponentsandconnectionsbetweencellshelpcoordinatecellularactivitiesExtracellularmatrix(ECM)

Theextracellularmatrixisthedefiningfeatureofconnectivetissueinanimals.AplantcellInplantcellsbutnotanimalcells:ChloroplastsCentralvacuoleandtonoplastCellwallPlasmodesmataCYTOSKELETONRibosomes(smallbrwondots)CentralvacuoleMicrofilamentsIntermediatefilamentsMicrotubulesRoughendoplasmicreticulumSmoothendoplasmicreticulumChromatinNUCLEUSNuclearenvelopeNucleolusChloroplastPlasmodesmataWallofadjacentcellCellwallGolgiapparatusPeroxisomeTonoplastCentrosomePlasmamembraneMitochondrionFigure6.9ThenucleusContainsmostofthegenesintheeukaryoticcell

(somegenesarelocatedinmitochondriaa