1-cell structure

Copyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.CHAPTER4LECTURESLIDESCellStructureChapter4Fibroblastcell3EukaryoticCells•Possessamembrane-boundnucleus•Morecomplexthanprokaryoticcells•Hallmarkiscompartmentalization–Achievedthroughuseofmembrane-boundorganellesandendomembranesystem•Possessacytoskeletonforsupportandtomaintaincellularstructure4Cells•Cellswerediscoveredin1665byRobertHooke•Earlystudiesofcellswereconductedby–MathiasSchleiden(1838)–TheodorSchwann(1839)•SchleidenandSchwannproposedtheCellTheory5CellTheory1.Allorganismsarecomposedofcells2.Cellsarethesmallestlivingthings3.Cellsariseonlyfrompre-existingcells•Allcellstodayrepresentacontinuouslineofdescentfromthefirstlivingcells6Cellsizeislimited•Mostcellsarerelativelysmallduerelianceondiffusionofsubstancesinandoutofcells•Rateofdiffusionaffectedby–Surfaceareaavailable–Temperature–Concentrationgradient–Distance7Surfacearea-to-volumeratio•Organismmadeofmanysmallcellshasanadvantageoveranorganismcomposedoffewer,largercells•Asacell’ssizeincreases,itsvolumeincreasesmuchmorerapidlythanitssurfacearea•Somecellsovercomelimitationbybeinglongandskinny–likeneurons8Thereisalwayseception！10Microscopes•Notmanycellsarevisibletothenakedeye–Mostarelessthan50μmindiameter•Resolution–minimumdistancetwopointscanbeapartandstillbedistinguishedastwoseparatepoints–Objectsmustbe100μmapartfornakedeyetoresolvethemastwoobjectsratherthanone2types•Lightmicroscopes–Usemagnifyinglenseswithvisiblelight–Resolvestructuresthatare200nmapart–Limittoresolutionusinglight•Electronmicroscopes–Usebeamofelectrons–Resolvestructuresthatare0.2nmapart11SizesofLivingThingsElectronmicroscopeLightmicroscope13Basicstructuralsimilarities1.NucleoidornucleuswhereDNAislocated2.Cytoplasm–Semifluidmatrixoforganellesandcytosol3.Ribosomes–Synthesizeproteins4.Plasmamembrane–Phospholipidbilayer14ProkaryoticCells•Simplestorganisms•Lackamembrane-boundnucleus–DNAispresentinthenucleoid•Cellwalloutsideofplasmamembrane•Docontainribosomes(notmembrane-boundorganelles)•Twodomainsofprokaryotes–Archaea–BacteriaBacterialcellwalls•Mostbacterialcellsareencasedbyastrongcellwall–composedofpeptidoglycan–Cellwallsofplants,fungi,andmostprotistsdifferent•Protectthecell,maintainitsshape,andpreventexcessiveuptakeorlossofwater•Susceptibilityofbacteriatoantibioticsoftendependsonthestructureoftheircellwalls•Archaealackpeptidoglycan1516171819Nucleus•Repositoryofthegeneticinformation•Mosteukaryoticcellspossessasinglenucleus•Nucleolus–regionwhereribosomalRNAsynthesistakesplace•Nuclearenvelope–2phospholipidbilayers–Nuclearpores–controlpassageinandout•Ineukaryotes,theDNAisdividedintomultiplelinearchromosomes–Chromatin，chromasome，nucleosome，DNA,histone21Ribosomes•Cell’sproteinsynthesismachinery•Foundinallcelltypesinall3domains•RibosomalRNA(rRNA)-proteincomplex•ProteinsynthesisalsorequiresmessengerRNA(mRNA)andtransferRNA(tRNA)•Ribosomesmaybefreeincytoplasmorassociatedwithinternalmembranes222324EndomembraneSystem•Seriesofmembranesthroughoutthecytoplasm•Dividescellintocompartmentswheredifferentcellularfunctionsoccur•Oneofthefundamentaldistinctionsbetweeneukaryotesandprokaryotes25Endoplasmicreticulum•Roughendoplasmicreticulum(RER)–Attachmentofribosomestothemembranegivesaroughappearance–Synthesisofproteinstobesecreted,senttolysosomesorplasmamembrane•Smoothendoplasmicreticulum(SER)–Relativelyfewboundribosomes–Varietyoffunctions–synthesis,storeCa2+,detoxification•RatioofRERtoSERdependsoncell’sfunction2627Golgiapparatus•Flattenedstacksofinterconnectedmembranes(Golgibodies)•Functionsinpackaginganddistributionofmoleculessynthesizedatonelocationandusedatanotherwithinthecellorevenoutsideofit•Cisandtransfaces•Vesiclestransportmoleculestodestination282930Lysosomes•Membrane-boundeddigestivevesicles•ArisefromGolgiapparatus•Enzymescatalyzebreakdownofmacromolecules•Destroycellsorforeignmatterthatthecellhasengulfedbyphagocytosis31Microbodies•Varietyofenzyme-bearing,membrane-enclosedvesicles•Peroxisomes–Containenzymesinvolvedintheoxidationoffattyacids–H2O2producedasby-product–renderedharmlessbycatalase3233Vacuoles•Membrane-boundedstructuresinplants•Variousfunctionsdependingonthecelltype•Therearedifferenttypesofvacuoles:–Centralvacuoleinplantcells–Contractilevacuoleofsomeprotists–Storagevacuoles3435Mitochondria•Foundinalltypesofeukaryoticcells•Boundbymembranes–Outermembrane–Intermembranespace–Innermembranehascristae–Matrix•Onthesurfaceoftheinnermembrane,andalsoembeddedwithinit,areproteinsthatcarryoutoxidativemetabolism•HavetheirownDNA3637Chloroplasts•Organellespresentincellsofplantsandsomeothereukaryotes•Containchlorophyllforphotosynthesis•Surroundedby2membranes•Thylakoidsaremembranoussacswithintheinnermembrane–Granaarestacksofthylakoids•HavetheirownDNA3839Endosymbiosis•Proposesthatsomeoftoday’seukaryoticorganellesevolvedbyasymbiosisarisingbetweentwocellsthatwereeachfree-living•Onecell,aprokaryote,wasengulfedbyandbecamepartofanothercell,whichwastheprecursorofmoderneukaryotes•Mitochondriaandchloroplasts4041Cytoskeleton•Networkofproteinfibe