2 Movement In and Out of Cells - Chaucer School…：2运动和细胞-乔叟学院…

Whatisdiffusion?DiffusionandconcentrationWhycanthestudentsmellthesockfromadistance?Thesockcanbesmeltbecausesweatandothermoleculesaremovingawayfromitandspreadingoutintheair.Thisiscalleddiffusion.Whereisthesmellstrongest?Thesmellisstrongestatthesock.Thesmellbecomesweakerfurtherawayfromthesock.MovingmoleculesInwhichstatesaremoleculesabletodiffuse?Moleculesinliquidsandgasesareconstantlymovingandbumpingintoeachother.Thismeansthattheytendtospreadout.gas(e.g.steam)liquid(e.g.water)solid(e.g.ice)Diffusioninaction:onegasDiffusioninaction:twogasesChangingconcentrationsTherateofdiffusiondependsonseveralfactors,suchasthedistancetheparticleshavetotravelandthedifferenceinconcentration.Moleculesdiffuseuntiltheyareevenlyspacedapartandequilibriumisreached.Duringdiffusionmoleculesmovefromanareaofhighconcentrationtoanareaoflowconcentration.Theyaresaidtomovedownaconcentrationgradient.Diffusionisapassiveprocesswhichmeansthatnoenergyisneeded.highconcentrationlowconcentrationDiffusion:trueorfalse?Whyisdiffusionimportanttolife?Diffusionisthemainwayinwhichsubstancesmoveovershortdistancesinorganisms.Whatsubstancesneedtomove?Oxygen,foodandwasteproductsaresomeofthesubstancesthatmovebydiffusion.Inanimals,howdothesevitalsubstancesgettowheretheyareneeded?Thesubstancesaretransportedinthebloodstream,fromwheretheycandiffuseinandoutofcells.DiffusionandbreathingBreathinginvolvestheexchangeofgasesinthelungs;aprocessthatoccursbydiffusion.Whathappenswhenyoubreathein?Oxygenininhaledairdiffusesthroughthelungsandintothebloodstream.Theoxygenisthentransportedthroughoutthebody.Carbondioxideisthewastegasproducedbyrespiration.Carbondioxidediffusesfrombodytissuesintothebloodstreamandisexhaledviathelungs.Wheredoesgasexchangetakeplaceinthelungs?StructuresoftherespiratorysystemCross-sectionthroughanalveolusdeoxygenatedblood(frombodytissues)oxygenatedblood(tobodytissues)airin/outAlveoliarethetinyairsacsattheendofthebronchioles,inwhichgasexchangeoccurs.alveoluscapillaryredbloodcellHowarealveoliadapted?Alveolihaveseveraladaptationsthathelptomakegasexchangeveryefficient:Theyareverythin–onlyonecellthick.Theyarecoveredbyanetworkoffinecapillaries,enablinggasestopassalmostdirectlybetweenthelungsandbloodstream.Theyaremoist,encouraginggasmoleculestoeasilydissolve.Theyhavealargecombinedsurfacearea,allowinglargeamountsofgasestobeexchangedwitheachbreath.Whathappensinthealveoli?DiffusionanddigestionDigestionbreaksdownlargefoodmoleculesintosmallermoleculessuchasglucose,aminoacidsandfattyacidsthatcanbeeasilyabsorbed.Carbohydrates,proteinsandfatsaremadeupoflargemoleculesthatcannotbereadilyabsorbedbythebody.Inwhichpartofthedigestivesystemismostfoodabsorbed?Smallfoodmoleculesareusuallyabsorbedinthe

smallintestine,diffusingacrosstheintestinewallandintothebloodstream.Howisthesmallintestineadapted?Thewallofthesmallintestineislinedwithmanytinyfinger-likeprojectionscalledvilli.Theseareverythinandincreasethesurfaceareaofthesmallintestine,bothofwhichincreasethespeedofdiffusion.bloodvesselscapillarynetworkvillussmallintestineDiffusionandthesmallintestineHowdoestheinitialconcentrationofdissolvedfoodmoleculesinthesmallintestinecomparewiththeconcentrationofthebloodinthevilli?Theconcentrationofdissolvedfoodmoleculesishigherinthesmallintestinethaninthebloodenteringthevillus.Thismeansthatthedissolvedfoodmoleculesdiffusefromthesmallintestineintotheblood,movingfromhighertolowerconcentration.glucoseDiffusionandtheplacentaTheplacentaisanorganthatdevelopsintheuterusoffemalemammalsduringpregnancy.Theumbilicalcordconnectstheplacentatothefetus.Theplacentaenablesnutrientsandoxygentopassfromthemothertothefetusbydiffusion,andwastesubstancestodiffusefromthefetusbacktothemother.Theplacentacanfilteroutcertainmoleculesandbacteria,butisunabletostopmanyharmfulsubstancessuchasalcohol,chemicalsandsometypesofvirusfromreachingthefetus.DiffusionandtheplacentaHowdoestheplacentawork?umbilical

cordbloodtomotherlowinO2/nutrients,highinCO2/wasteumbilical

arteryumbilical

veinplacentalvilli

increasesurfaceareafordiffusionbloodfrommotherhighinO2/nutrients,lowinCO2/wasteDiffusionandnervesimpulsesnerveimpulseneurotransmitterreceptorsynapticcleftAsynapseisajunctionbetweentwoneuronesacrosswhichelectricalsignalsmustpass.Neurotransmittermoleculesdiffusefromvesiclestowardstheneurotransmitterreceptors,movingfromanareaofhighconcentrationtolowconcentration.neurotransmitterWhatisosmosis?waterglucosepartially-

permeablemembrane(viskingtubing)Osmosisisthediffusionofwatermolecules

fromalowconcentrationsolutiontohighconcentrationsolution,acrossapartially-permeablemembrane.Apartially-permeablemembranehasholesinitthatpermitwatermoleculesthroughbutaretoosmalltoallowlargermoleculesthrough.Osmosiscanbedemonstratedusingviskingtubingfilledwithasolutionandplacedinabeakerofpurewater.Dilutevs.concentratedConcentratedsolutionshavealowconcentrationofwatermolecules.Dilutesolutionshaveahighconcentrationofwatermolecules.Duringosmosis,watermoleculesdiffusefrompurewaterordilutesolutiontomoreconcentratedsolutions.purewaterdilutesolutionconcentratedsolutionPredictingosmosisOsmosisinactionOsmosisandcellsPlantandanimalcellsaresurroundedbyapartially-permeableplasmamembrane.Thisallowswaterandothersmallmoleculestodiffuseacross.plantcellredbloodcellcellwallPlantcellsadditionallyhaveastrongcellwallsurroundingthemembranewhichofferssupportandprotection.plasmamembraneOsmosisandplantcellsOsmosisandanimalcellsAnimalcellsdonothaveacellwall.Thismeanstheyresponddifferentlytoplantcellstothegainandlossofwater.Inconcentratedsolutions,waterlosscausesthecellstoshrink.Whenthishappenstoredbloodcells,itiscalledcrenation.Indilutesolutions,osmosiscancauseanimalscells,suchasredbloodcells,toswellupandburst.Thisiscalledlysis.OsmosisandanimalcellsOsmosisandanimalcellsInordertoremainhealthy,animalcellsneedtomaintainanisotonicwaterbalance.Thismeansthatthewaterconcentrationbothinsideandoutsidethecellareequal.Theconcentrationofwaterandsaltinthebloodarecontrolledbythekidneys.Thekidneysarecontrolledbytheportionofthebraincalledthehypothalamus.hypothalamusMovementinandoutofcellsSubstancesmoveinandoutofcellbypassiveandactivetransport.Whichmethodsoftransportareillustrated?Whatisactivetransport?Substancescanmovepassivelyinandoutofcellsbydiffusionuntiltheconcentrationonbothsidesofthecellmembranereachesanequilibrium.Substancescancontinuetomoveinandoutofacellusingaprocesscalledactivetransport.Asthenamesuggests,activetransportrequiresenergyfromthecell,whichismadeavailablebyrespiration.Duringactivetransport,proteincarriersinthecellmembrane‘pickup’particlesandmovethemagainsttheconcentrationgradient.Whatisactivetransport?ActivetransportinplantsPlantsneedtoabsorbmineralelementssuchasnitrogen,phosphorusandpotassiumfromthesoilforhealthygrowth.Whentheconcentrationofmineralsinsoilislowerthaninsidetheplant,activetransportisusedtoabsorbthemineralsagainsttheconcentrationgradient.Whatwouldhappeniftheplantreliedondiffusiontoabsorbminerals?Thecellswouldbecomedrainedofmineralsbecausetheywouldtraveldowntheconcentrationgradient.mineralsActivetransportinhumansDuringdigestion,thevilliinthesmallintestineabsorbthesolublenutrients.Overtime,theconcentrationofnutrientsinthevillireachanequilibriumwiththeconcentrationinthegut.Activetransportisusedtocontinuethetransportofthesmallamountsofremainingnutrientsagainsttheconcentrationgradient.glucoseGlossary(1/2)activetransport–Themovementofmoleculesagains