Features - Unknown - Prokaryotic Cell Features

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1、ProkaryoticCellFeaturesSizeThesmallsizeofprokaryoticcellsaffectstheirphysiology,growthrate,andecology.Duetotheirsmallcellsize,mostprokaryoteshavethehighestsurfacearea–to–volumeratioofanycells.Thischaracteristicaidsinnutrientandwasteexchangewiththeenvironment.Asacellincreasesinsize,itss

2、urfacearea-to-volumeratiodecreasesForasphere,S/V=3/rProkaryotesmaintainahighsurfaceareatovolumeratiobytheirsmallness.1.TRANSPORTRATE:Efficienttransportofrawmaterialsinandwastesout2.GROWTHRATE:Nutrientexchangelimitsgrowthrates.Manyprokaryotes=highmetabolicactivity(fastgrowth,reproductiv

3、erate).3.EVOLUTIONARYRATE:Giventhesameamountofnutrients,smallcellscanhavemoreindividualsinapopulationthanlargercells.Thus,morecelldivision,andmoremutation,moreevolutionarychange.Eukaryoteslargercellsize(ingeneral)Differentanswersforthetransportproblem1.lotsofinternalmembranechannels,in

4、vaginationsandsurfacearea2.cytoplasmicstreaming3.organelles(compartmentalizecellfunctions)4.bulkuptake-endocytosis(phagocytosis/pinocytosis)IntroducingaprokaryotethatisonemilliontimesbiggerthanE.coli!Sturgeonfishsymbiont.Epulopisciumfiseloni600µm(0.6mm)long20-40µmlongIndividualflagella

5、twisttogethertoform“thick”flagellaLargestknownbacterium:ThiomargaritanamibiensisSomenearly1mmwideLargecentralvacuole(dark)containsnitratesequesteredtouseintheoxidationofreducedsulfurcompounds.Stringofpearls:reflectivesulfurgranulesHowdoweseemicrobes?1.LightMicroscopyUpto1,500Xmagnifica

6、tion(yoursinlab:1000X)Limitofresolvingpoweris~0.2µM,orabout1/3thewidthofanaveragebacterialcellLightgatheringabilitydecreasesasmagnificationincreasesImmersionoilhelpsgatherlightraysthatwouldotherwisebelostfromspecimenHowdoweseemicrobes?2.ElectronMicroscopy(EM):Upto1,000,000Xmagnificatio

7、n(1,000Xmorethanlightmicroscope)“Light”=>electronbeam“Lenses”=>electromagnetstofocusbeamLimitofresolvingpoweris~0.2nm(molecules)CanseeinternalstructuresandexternalappendagesLimitsofResolutionFigure4.3ComparingProkaryoticandEukaryoticCellsComparingProkaryoticandEukaryoticCellsComparet