b3bdiffusion(扩散运动).ppt

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1、B3bDiffusion1.Describediffusionasthemovementofasubstancefromaregionofhightolowconcentration.Describehowmoleculesenterandleavecellsbydiffusionthroughthecellmembrane(highertier)Explainthatdiffusionisthenetmovementofparticlesfromanareaofhighconcentrationtoa

2、nareaoflowconcentrationandisaconsequenceoftherandommovementofindividualparticlesExplainthattherateofdiffusionisaffectedby:distance,concentrationdifference(gradient),surfacearea2.Describehowsmalldigestedfoodmoleculesareabsorbedintothebloodinthesmallintest

3、inebydiffusion3.Describegaseousexchangewithinalveolibetweenairandblood(highertier)Explainhowthealveoliareadaptedforefficientgaseousexchange:permeable,moist,largesurfacearea,goodbloodsupply,wallonecellthickExplainhowthesmallintestineisadaptedfortheabsorpt

4、ionoffood:long,largesurfacearea(villiandmicrovilli),permeablesurface,goodbloodsupply4.Describehowfoodandoxygenreachthefoetus,andcarbondioxideandotherwastesareremoved,bydiffusionthroughtheplacenta(highertier)Explainhowtheplacentaisadaptedtoincreasetherate

5、ofdiffusion(highertier)Explainhowtransmittersubstancesdiffuseacrosssynapsestocarrysignalsfromoneneuronetoanother5.Describehowcarbondioxideandoxygendiffuseinandoutofplantsthroughtheleaves(highertier)Explainhowleavesareadaptedtoincreasetherateofdiffusionof

6、carbondioxideandoxygen6.ExplainthelossofwaterfromleavesintermsofthediffusionofwatermoleculesWhatisdiffusion?DiffusionandconcentrationWhycanthestudentsmellthesockfromadistance?Thesockcanbesmeltbecausesweatandothermoleculesaremovingawayfromitandspreadingou

7、tintheair.Thisiscalleddiffusion.Whereisthesmellstrongest?Thesmellisstrongestatthesock.Thesmellbecomesweakerfurtherawayfromthesock.MovingmoleculesInwhichstatesaremoleculesabletodiffuse?Moleculesinliquidsandgasesareconstantlymovingandbumpingintoeachother.T

8、hismeansthattheytendtospreadout.gas(e.g.steam)liquid(e.g.water)solid(e.g.ice)Diffusioninaction:onegasDiffusioninaction:twogasesChangingconcentrationsTherateofdiffusiondependsonseveralfactors,suchasthedistancetheparticlesha