基础微生物学课件公开课一等奖课件省课获奖课件

微生物吸取营养物质方式第1页1、单纯扩散(simplediffusionorpassivediffusion)被输送物质，靠细胞内外浓度为动力，以透析或扩散形式从高浓度区向低浓度区扩散。Simplediffusionmeansthatthemoleculescanpassdirectlythroughthemembrane.Diffusionisalwaysdownaconcentrationgradient.Thislimitsthemaximumpossibleconcentrationofthemoleculeinsidethecell(oroutsidethecellifitisawasteproduct).Theeffectivenessofdiffusionisalsolimitedbythediffusionrateofthemolecule.Therefore,thoughdiffusionisaneffectiveenoughtransportmechanismforsomesubstances(suchasH2O),thecellmustutilizeothermechanismsformanyofitstransportneeds.第2页1、单纯扩散(simplediffusionorpassivediffusion)特点：①扩散是非特异性营养物质吸取方式：如营养物质通过细胞膜中含水小孔，由高浓度胞外环境向低浓度胞内扩散；②在扩散过程中营养物质构造不发生变化：即既不与膜上分子发生反应，本身分子构造也不发生变化；③物质运输速率较慢：速率与胞内外营养物质浓度差有关，即随细胞膜内外该物质浓度差减少而减小，直到胞内外物质浓度相同；④不需要载体参与；

扩散是一种不需要代谢能运输方式：因此，物质不能进行逆浓度运输。⑤可运输养料有限：限于水、溶于水气体，及分子量小，脂溶性、极性小营养物质。第3页smosisflowstowardshighsaltconcentrations第4页单纯扩散模式图细胞膜外细胞膜内细胞膜第5页三营养物通过与细胞膜上载体蛋白（也称作透过酶permease）可逆性结合来加快其传递速度促进扩散

(facilitateddiffusion/transport)Facilitateddiffusionutilizesmembraneproteinchannelstoallowchargedmolecules(whichotherwisecouldnotdiffuseacrossthecellmembrane)tofreelydiffuseinandoutofthecell.ThesechannelscomesintogreatestusewithsmallionslikeK+,Na+,andCl-.Thespeedoffacilitatedtransportislimitedbythenumberofproteinchannelsavailable,whereasthespeedofdiffusionisdependentonlyontheconcentrationgradient.第6页促进扩散(facilitateddiffusion)特点：在促进扩散过程中营养物质本身在分子构造上也不会发生变化不消耗代谢能量，故不能进行逆浓度运输运输速率由胞内外该物质浓度差决定需要细胞膜上载体蛋白（透过酶）参与物质运输被运输物质与载体蛋白有高度特异性养料浓度过高时,与载体蛋白出现饱和效应促进扩散运输方式多见于真核微生物中，例如一般在厌氧生活酵母菌中，某些物质吸取和代谢产物分泌是通过这种方式完成。第7页Embededprotein:第8页第9页Proteins

thatactascarriers

aretoolargetomoveacrossthemembrane.Theyaretransmembraneproteins.Theycyclebetweentwoconformationsinwhichasolutebindingsiteisaccessibleononesideofthemembraneortheother.第10页促进扩散模式图细胞膜细胞膜外细胞膜内恢复原构象移位再循环结合结合构象变化第11页oractiveansport

第12页积极运输(Activetransport)在代谢能推进下，通过膜上特殊载体蛋白逆养料浓度梯度吸取营养物质过程第13页积极运输(Activetransport)特点：物质在积极运输过程中需要消耗代谢能能够进行逆浓度运输运输方式需要载体蛋白参与对被运输物质有高度立体专一性被运输物质在转移过程中不发生任何化学变化不一样微生物在积极运输过程中所需能量起源不一样，好氧微生物中直接来自呼吸能，厌氧微生物主要来自化学能，光合微生物中则主要来自光能。积极运输是微生物吸取营养物质主要方式。第14页

Comparisonofpassiveandactivetransport.

Legend:Ifunchargedsolutesaresmallenough,theycanmovedowntheirconcentrationgradientsdirectlyacrossthelipidbilayeritselfbysimplediffusion.Examplesofsuchsolutesareethanol,carbondioxide,andoxygen.Mostsolutes,however,cancrossthemembraneonlyifthereisamembranetransportprotein(acarrierproteinorachannelprotein)totransferthem.Asindicated,passivetransport,inthesamedirectionasaconcentrationgradient,occursspontaneously,whereastransportagainstaconcentrationgradient(activetransport)requiresaninputofenergy.Onlycarrierproteinscancarryoutactivetransport,butbothcarrierproteinsandchannelproteinscancarryoutpassivetransport.第15页第16页积极运输模式图细胞膜细胞膜外细胞膜内恢复原构象移位再循环结合构象变化ADP+PiATP第17页Na+-K+-ATP酶系统Na+-K+-ATPase是存在于原生质膜上一种主要离子通道蛋白功能:利用ATP能量将Na+由细胞内“泵”出胞外,并将K+“泵”入胞内。该酶由大小两个亚基组成（MW:12万,5.5万）第18页作用步骤:1.ATP酶(E)在细胞内侧与3个Na+结合,同步消耗能量;2.磷酸化ATP酶(E+)构象变化将Na+排除胞外,并与2个K+

结合;3.K+激发E+脱磷酸化恢复为E,同步将K+运入细胞.第19页第20页

基因转位是一种特殊积极运输，与一般积极运输相比，营养物质在运输过程中发生了化学变化（糖在运输过程中发生了磷酸化）。其他特点与积极运输相同。基因转位主要存在于厌氧和兼性厌氧型细菌中，也主要是用于单（或双）糖与糖衍生物，以及核苷与脂肪散运输基团转位(Grouptranslocation)第21页在酶Ⅰ作用下HPr被激活在酶Ⅱ作用下P-HPr将磷酸转移给糖第22页运输机制:是依靠磷酸转移酶系统,即磷酸烯醇式丙酮酸-己糖磷酸转移酶系统.运输步骤:1.热稳载体蛋白(HPr)激活

细胞内高能化合物磷酸烯醇式丙酮酸（PEP）磷酸基团把HPr激活。酶1

PEP+HPr丙酮酸+P-HPrHPr是一种低分子量可溶性蛋白，结合在细胞膜上，具有高能磷酸载体作用。第23页2、糖被磷酸化后运入膜内膜外环境中糖先与外膜表面酶2结合，再被转运到内膜表面。这时，糖被P-HPr上磷酸激活，并通过酶2作用将糖-磷酸释放到细胞内。酶2

P-HPr+糖糖-P+HPr酶2是一种结合于细胞膜上蛋白，它对底物具有特异性选择作用，因此细胞膜上可诱导出一系列与底物分子对应酶2。第24页基团移位模式图细胞膜外细胞膜内SSSS细胞膜Enz2Enz2Enz2Enz2SSHPrP~PHPr~Enz1+PEP丙酮酸第25页四种运输营养物质方式比较比较项目单纯扩散促进扩散积极运输基团转位特异载体蛋白运输速度物质运输方向胞内外浓度运输分子能量消耗运输后物质构造无慢由浓至稀相等无特异性不需要不变有快由浓至稀相等特异性不需要不变有快由稀至浓胞内浓度高特异性需要不变有快由稀至浓胞内浓度高特异性需要变化第26页SpecialCases1.

Endocytosis2.

Exocytosis第27页Therearefourtypesofcarrier-mediatedtransportsystemsinprocaryotes.Thecarrierisaprotein(orgroupofproteins)thatfunctioninthepassageofasmallmoleculefromonesideofamembranetoanother.Atransportsystemmaybeasingletransmembranousproteinthatformsachannelthatadmitspassageofaspecificsolute.Oratransportsystemmaybeacoordinatedsystemofproteinsthatbindsandsequentiallypassesasmallmoleculethroughmembrane.Transportsystemshavethepropertyofspecificityforthesolutetransported.Sometransportsystemstransportasinglesolutewiththesamespecificityandkineticsasanenzyme.Sometransportsystemswilltransport(structurally)relatedmolecules,althoughatreducedefficiencycomparedtotheirprimarysubstrate.Mosttransportsystemstransportspecificsugars,aminoacids,anionsorcationsthatareofnutritionalvaluetothebacterium.第28页Figure12.Transportprocessesinbacterialcells.Solutesenterorexitfrombacterialcellsbymeansofoneofthreeprocesses:uniport,symport(alsocalledcotransport)andantiport(alsocalledexchangediffusion).Transportsystems(Figure13below)operatebyoneoranotheroftheseprocesses.第29页第30页Facilitateddiffusionsystems(FD)aretheleastcommontypeoftransportsysteminbacteria.Actually,theglyceroluniporterinE.coliistheonlywellknownfacilitateddiffusionsystem.FDinvolvesthepassageofaspecificsolutethroughacarrierthatformsachannelinthemembrane.Thesolutecanmoveineitherdirectionthroughthemembranetothepointofofequilibriumonbothsidesofthemembrane.Althoughthesystemiscarrier-mediatedandspecific,noenergyisexpendedinthetransportprocess.Forthisreasontheglycerolmoleculecannotbeaccumulatedagainsttheconcentrationgradient.Facilitateddiffusionsystems(FD)第31页Iondriventransportsystems(IDT)andBinding-proteindependenttransportsystems(BPDT)areactivetransportsystemsthatareusedfortransportofmostsolutesbybacterialcells.IDTisusedforaccumulationofmanyionsandaminoacids;BPDTisfrequentlyusedforsugarsandaminoacids.IDTisasymportorantiportprocessthatusesahydrogenion(H+)i.e.,protonmotiveforce(pmf),orsomeothercation,i.e.,chemiosmoticpotential,todrivethetransportprocess.IDTsystemssuchasthelactosepermeaseofE.coliutilizetheconsumptionofahydrogenionduringthetransportoflactose.Thustheenergyexpendedduringactivetransportoflactoseisintheformofpmf.Thelactosepermeaseisasingletransmembranouspolypeptidethatspansthemembraneseventimesformingachannelthatspecificallyadmitslactose.第32页Binding-proteindependenttransportsystems,suchasthehistadinetransportsysteminE.coli,arecomposedoffourproteins.Twoproteinsformamembranechannelthatallowspassageofthehistadine.Athirdproteinresidesintheperiplasmicspacewhereitisabletobindtheaminoacidandpassittoaforthproteinwhichadmitstheaminoacidintothemembranechannel.Drivingthesolutethroughthechannelinvolvestheexpenditureofenergy,whichisprovidedbythehydrolysisofATP.第33页Grouptranslocationsystems(GT),morecommonlyknownasthephosphotransferasesystem(PTS)inE.coli,areusedprimarilyforthetransportofsugars.Likebindingprotein-dependenttransportsystems,theyarecomposedofseveraldistinctcomponents.However,GTsystemsspecificforonesugarmaysharesomeoftheircomponentswithothergrouptransportsystems.InE.coli,glucosemaybetransportedbyagrouptranslocationprocessthatinvolvesthephosphotransferasesystem.Theactualcarrierinthemembraneisaproteinchannelfairlyspecificforglucose.Glucosespecificallyentersthechannelfromtheoutside,butinordertoexitintothec