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1、（生物科技行业）细胞生物学双语教案(线粒体结构与功能)细胞生物学双语教案3（线粒体结构和功能）MitochondrialSubstructureMitochondriacontaintwomembranes,separatedbyaspace.Botharethetypicalunitmembrane(railroadtrack)instructure.Insidethespaceenclosedbytheinnermembraneisthematrix.ThisappearsmoderatelydenseandonemayfindstrandsofDNA,ribosomes,orsmallg
2、ranulesinthematrix.Themitochondriaareabletocodeforpartoftheirproteinswiththesemoleculartools.Theabovecartoonshowsthediagramofthemitochondrialmembranesandtheenclosedcompartments.Howaremitochondriaorganizedtobepowerhouses?Thefoodweeatisoxidizedtoproducehigh-energyelectronsthatareconvertedtostoredenerg
3、y.Thisenergyisstoredinhighenergyphosphatebondsinamoleculecalledadenosinetriphosphate,orATP.ATPisconvertedfromadenosinediphosphatebyaddingthephosphategroupwiththehigh-energybond.Variousreactionsinthecellcaneitheruseenergy(wherebytheATPisconvertedbacktoADP,releasingthehighenergybond)orproduceit(whereb
4、ytheATPisproducedfromADP).Stepsfromglycolysistotheelectrontransportchain.Whyaremitochondriaimportant?LetsbreakdowneachofthestepssoyoucanseehowfoodturnsintoATPenergypacketsandwater.Thefoodweeatmustfirstbeconvertedtobasicchemicalsthatthecellcanuse.Someofthebestenergysupplyingfoodscontainsugarsorcarboh
5、ydrates.bread,forexample.Usingthisasanexample,thesugarsarebrokendownbyenzymesthatsplitthemintothesimplestformofsugarwhichiscalledglucose.Then,glucoseentersthecellbyspecialmoleculesinthemembranecalled“glucosetransporters”.Onceinsidethecell,glucoseisbrokendowntomakeATPintwopathways.Thefirstpathwayrequ
6、iresnooxygenandiscalledanaerobicmetabolism.Thispathwayiscalledglycolysisanditoccursinthecytoplasmoutsidethemitochondria.Duringglycolysis,glucoseisbrokendownintopyruvate.Otherfoodslikefatscanalsobebrokendownforuseasfuel(seefollowingcartoon).Eachreactionisdesignedtoproducesomehydrogenions(electrons)th
7、atcanbeusedtomakeenergypackets(ATP).However,only4ATPmoleculescanbemadebyonemoleculeofglucoserunthroughthispathway.Thatiswhymitochondriaandoxygenaresoimportant.WeneedtocontinuethebreakdownprocesswiththeKrebscycleinsidethemitochondriainordertogetenoughATPtorunallthecellfunctions.Theeventsthatoccurinsi
8、deandoutsidemitochondriaarediagrammedintheabovecartoon.PyruvateiscarriedintothemitochondriaandthereitisconvertedintoAcetylCo-AwhichenterstheKrebscycle.Thisfirstreactionproducescarbondioxidebecauseitinvolvestheremovalofonecarbonfromthepyruvate.HowdoestheKrebscyclework?Thewholeideabehindrespirationint
9、hemitochondriaistousetheKrebscycle(alsocalledthecitricacidcycle)togetasmanyelectronsoutofthefoodweeataspossible.Theseelectrons(intheformofhydrogenions)arethenusedtodrivepumpsthatproduceATP.TheenergycarriedbyATPisthenusedforallkindsofcellularfunctionslikemovement,transport,entryandexitofproducts,divi
10、sion,etc.Thefollowingexplanationisverysimpleandfocusesononlythepathwayfrompyruvatethroughthecycle.However,itillustratestheprocessanditsfunctions.ToruntheKrebscycle,youneedseveralimportantmoleculesinadditiontoalltheenzymes.Consultyourtextfordetailsabouttheenzymesthemselves.Thispresentationwillfocuson
11、theelectrondonors,carriersandacceptors.First,youneedpyruvate,whichismadebyglycolysisfromglucose.Next,youneedsomecarriermoleculesfortheelectrons.Therearetwotypesofthese:oneiscallednicotinamideadeninedinucleotide(NAD+)andtheotheriscalledflavinadeninedinucleotide(FAD+).Thethirdmolecule,ofcourse,isoxyge
12、n.Pyruvateisa3carbonmolecule.Afteritentersthemitochondria,itisbrokendowntoa2carbonmoleculebyaspecialenzyme(seetextformoredetailsaboutthebiochemistryofeachstep).Thisreleasescarbondioxide.The2carbonmoleculeiscalledAcetylCoAanditenterstheKrebscyclebyjoiningtoa4carbonmoleculecalledoxaloacetate.Oncethetw
13、omoleculesarejoined,theymakea6carbonmoleculecalledcitricacid(2carbons+4carbons=6carbons).ThatiswheretheCitricacidcyclegotitsname.fromthatfirstreactionthatmakescitricacid.Citricacidisthenbrokendownandmodifiedinastepwisefashion(seetextfordetails)and,asthishappens,hydrogenionsandcarbonmoleculesarerelea
14、sed.ThecarbonmoleculesareusedtomakemorecarbondioxideandthehydrogenionsarepickedupbyNADandFAD(seebelow).Eventually,theprocessproducesthe4carbonoxaloacetateagain.Thereasontheprocessiscalledacycle,isbecauseitendsupalwayswhereitstarted.withoxaloacetateavailabletocombinewithmoreacetylcoA.Whatis“oxidative
15、phosphorylation”?First,somebasicdefinitions.Whenyoutakehydrogenionsorelectronsawayfromamolecule,you“oxidize”thatmolecule.Whenyougivehydrogenionsorelectronstoamolecule,you“reduce”thatmolecule.Whenyougivephosphatemoleculestoamolecule,you“phosphorylate”thatmolecule.So,oxidativephosphorylation(verysimpl
16、y)meanstheprocessthatcouplestheremovalofhydrogenionsfromonemoleculeandgivingphosphatemoleculestoanothermolecule.Howdoesthisapplytomitochondria?AstheKrebscycleruns,hydrogenions(orelectrons)aredonatedtothetwocarriermoleculesin4ofthesteps.TheyarepickedupbyeitherNADorFADandthesecarriermoleculesbecomeNADHandFADH(becausetheynowarecarryingahydrogenion).Thefollowingcartoonshowswhathappensnext.Theseelectronsarecarriedchemicallytotherespiratoryorel
