中大细胞生物学课前训练题.docx
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中大细胞生物学课前训练题.docx
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中大细胞生物学课前训练题
2006细胞课Q&A·Q
Bydaisy
2006.9.5
1.Yournext-doorneighborhasdonated$20insupportofcancerresearchandinhorrifiedtolearnthathermoneyisbeingspentonstudyingbrewer’syeast.Howcouldyouputhermindatease?
(1)、参考答案:
为什么你的邻居会有这种担心?
(2)、参考答案:
为什么要假设?
2.anadulthumaniscomposedofabout1013cells,allofwhicharederivedbycelldivisionfromasinglefertilizedegg.
A.Assumingthatallcellscontinuetodivide(likebacteriainrichmedia).Howmanygenerationsofcelldivisionswouldberequiredtoproduce1013cells?
B.Humancellsinculturedivideaboutonceperday.Assumingallcellscontinuetodivideatthisrateduringdevelopment,howlongwouldittaketogenerateanadultorganism?
C.Whyisit,doyouthink,thatadulthumantakelongertodevelopthancalculationsmightsuggest?
2006.9.12
1.FriedrichMiescher(1844-1895),GregorMendel(1822-1884),LouisPasteur(1822-1895),andRudolfVirchow(1821-1902)wereEuropeanscientists(fromSwitzerland,Austria,France,andGermany,respectively)whosemostimportantdiscoveriesweremadeinthe20-yearperiodfrom1855to1875.assumethatthefourmenmetatascientificconferencein1875todiscusstheirrespectivecontributionstobiology.
(a)Whatmightthefourscientistshavefoundtheyhadincommon?
(b)WhatdoyouthinkPasteurmighthavefoundmostintriguingorrelevantaboutVirchow’swork?
Explainyouranswer.
(c)WhatdoyouthinkVirchowmighthavefoundmostintriguingorrelevantaboutMendel’swork?
Explainyouranswer.
(d)InwhoseworkdoyouthinkMieschermighthavebeenthemostinterested?
Explainyouranswer.
答:
(a)Thefourscientistsmighthavefoundthattheyhadcommoninterestsintheoriginofcells(frompreexistingcells,notby“spontaneousgeneration")andthenatureofthegeneticinformationthatorganismspassontotheirprogeny.(Bearinmind,however,thatweareansweringthequestionfromtheperspectiveofalmost125yearsoffurtherdiscoveriesandinsights.In1875,thefourscientistsmightwithequallikelihoodhaveconcludedthattheyhadfew,ifany,interestsincommon.)
(b)GivenPasteur’sdemonstrationthatliving,preexistingyeastcellsareneededtocarryoutthefermentationofsugarintoalcohol,hewouldalmostcertainlyhavebeeninterestedinVirchow’sconclusionthatallcellscomefrompreexistingcells.(Infact,hewouldmostlikelyhavefoundVirchow’sadditiontothecelltheoryofSchleidenandSchwannparticularlyencouraginginlightoftheearlierbelief,debunkedbyPasteur’swork,thatyeastcellsaroseby“spontaneousgeneration"inthepresenceofsuchsubstratesasfermentablegrapejuice.)
(c)InlightofVirchow’sconclusionthatcells(andthereforeorganismsaswell,presumably)ariseonlyfrompreexistingcells,hewouldlikelyhavebeenveryinterestedinMendel’sevidencethattraitssuchasthoseheobservedinpeaplantswereheritableandcouldbepassedfromonegenerationtothenextbytransmissionof“hereditaryfactors,"becausethegeneticcontinuitybetweengenerationsimpliedbyMendel’sfindingswouldhavefitwellwiththephysicalcontinuityofgenerationsinherentinVirchow’scontributiontocelltheory.
(d)IfMiescherweresufficientlyforesighted,hemighthavebeenmostinterestedintheworkofMendelbecauseMiescher’sdiscoveryofwhatwenowcallDNAwaseventuallytoprovidethechemicalbasisfortheheritabilityoftraitsdescribedbyMendel.
2006.9.19
1.Youarestudyingthebindingofproteinstothecytoplasmicfaceofculturedneuroblastoma(神经母细胞瘤)cellsandhavefoundamethodthatgivesagoodyieldofinside-outvesiclesfromtheplasmamembrane.Unfortunately,yourpreparationsarecontaminatedwithvariableamountsofright-side-outvesicles.Nothingyouhavetriedavoidsthisvariablecontamination.
Afriendsuggeststhatyoupassyourvesiclesoveranaffinitycolumnmadeoflectincoupledtosolidbeads.Whatisthepointofyourfriend’ssuggestion?
回答关键词:
膜糖仅存在于外膜,凝集素与糖亲和,亲和层析的方法。
2.Proteinsthatspanamembraneasanαhelixhaveacharacteristicstructureintheregionofthebilayer.Whichofthethree20-aminoacidsequenceslistedbelowisthemostlikelycandidateforsuchatransmembranesegment?
Explainthereasonsforyourchoice.
A.ITLIYFGVMAGVIGTILLIS
B.ITPIYFGPMAGVIGTPLLIS
C.ITEIYFGRMAGVIGTDLLIS
Answer:
A.跨膜蛋白需疏水。
2006.9.26
Whenpresentintheculturemedium,ouabain(乌本苷)inhibitstheNa+/K+ATPaseinculturedcells.Butwhenthedrugismicroinjectedintocells,itexertsnoinhibitoryeffect.AlthoughouabainitselfpossessesnonegativechargeouabaintreatmentcausestheαsubunitsoftheNa+/K+ATPasetobecomemorenegativelychargedbutdoesn’talterthechargepropertiesoftheβsubunits.
a.OnwhichsideoftheplasmamembranearetheouabainandATP-bindingsitesoftheenzymelocated?
b.Duringthetransportprocess,theNa+/K+ATPasebecomestransilentlyphosphorylated.Whatdotheseobservationssuggestaboutalikelymechanismforouabaininhibitionofthisionpump?
c.Whichofthetwosubunits,αorβ,ismostlikelytobephosphorylated……?
A、外侧。
B、抑制去磷酸化。
C、α。
2006.10.10
1.Cadherinsareknowntomediatehomophilicinteractionsbetweencells,whatisahomophilicinteractionandhowcanthisbedemonstratedexperimentallyforE-andP-cadherins?
2.Proteoglycansarecharacterizedbytheabundanceofnegative.Chargesontheirsugargroups,howwouldthepropertiesofthesecompoundsdifferifthenegativechargeswerecutasabundant?
2006.10.17
1.Gapjunctionsaredynamicstructuresthat,likeconventionalionchannels,aregated:
theycanclose,byareversibleconformationalchangeinresponsetochangesinthecell.Thepermeabilityofgapjunctionsdecreaseswithinseconds,forexample,whentheintracellularCa2+israised.Speculatewhythisformofregulationmightbeimportantforthehealthofatissue.
2.CancerouslivercellscanberestoredtotheirnormalgrowthbyinsertingthegeneforE-cadherin.Thisindicatesthatcadherinisinvolvedin
a.Formationoftheextracellularmatrix.
b.Openingvoltage-gatedchannels.
c.ActivationofcAMP.
d.Cellmigration.
e.Noneoftheabove.
Answer:
D.
2006.10.24
1.WhydoyousupposecellshaveevolvedintracellularCa2+storesevenifextracellularCa2+isusuallynotlimiting?
2.Hypertensionorhighbloodpressure,isoftenseeninelderlypeople.Atypicalprescriptiontoreduceapatient’sbloodpressureuncludescompoundscalledβ-blockers,whichblockβ-adrenergic(肾上腺素能)receptorsthrough-outthebody.Thesereceptorsbindsepinephrinetherebyactivatingacellularresponse.Whydoyouthinkβ-blockersareeffectiveinreducingbloodpressure?
2006.10.31
1.Latentgeneregulatoryproteinsarepreventedfromenteringthenucleusuntilthecellreceivesanappropriatesignal.Listfourwaysbywhichcellskeepgeneregulatoryproteinsoutofthenucleus,andgiveanexampleofalatentgeneregulatoryproteinthatiscontrolledbyeachmechanism.
2.Dinitrophenol(二硝基苯酚,DNP)isasmallmoleculethatrendersmembranespermeabletoprotons.Inthe1940s,smallamountsofthishighlytoxiccompoundweregiventopatientstoinduceweightloss.DNPwaseffectiveinproducingweightloss,especiallylossoffatreserves.Canyouexplainhowitmightcausesuchloss?
2006.11.7
1.Whentheantibioticvalinomycin(isaddedtoactivelyrespiringmitochondria,severalthingshappen:
theyeiledofATPdecreasestherateofO2consumptionincreases,heatisreleased,andthepHgradientacrosstheinnermitochondriamembraneincreases.Doesvalinomycinactasanuncoupleroraninhibitorofoxidativephosphorylation?
Explaintheexperimentalobservationsintermsoftheantibiotic’sabilitytotransferK+ionsacrosstheinnermitochondriamembrane.
解偶联剂。
2.Primaryhyperoxaluriatype1(pH1)isalethalautosomalrecessivedisease,causedbyadeficiencyoftheliver-specificperoxisomalenzymealanine;glyoxylute(乙醛酸)aminotransferase(AGT).Aboutone-thirdofpH1patientspossesssignificantlevelsofAGTproteinandtheirAGTcontainstwocriticalsingleaminoacidchanges:
onethatinterfereswithperoxisomaltargetingandasecondthatallowstheN-terminustoformanamphipathicαhelixwithapositivelychargedside.WheredoyousupposethismutantAGTisfoundincellsfromthesepatients?
Explainyourreasoning.
2006.11.14
1.Toaidyourstudiesofproteinimportintomitochondria,youtreatyeastcellswithcycloheximide(放线菌酮),whichblocksribosomemovementalongmRNA.Whenyouexaminethesecellsintheelectronmicroscope,youaresurprisedtofindcytosolicribosomesattachedtotheoutsideofthemitochondria.Bycontast,youhaveneverseenattachedribosomesintheabsenceofcycloheximide.
Toinvestigatethisphenomenonfurther,youpreparemitochondriafromcellsthathavebeentreatedwithcycloheximideandthenextractthemRNAthatisboundtotheribosomesassociatedwiththemitochondria.YoutranslatethismRNAinvitroandcomparetheproteinproductswithsimilarlytranslatedmRNAfromthecytosol.Theresultsareclear-out:
themitochondria-associatedribosomesaretranslatingmRNAsthatencodemitochondriaproteins.
Youareastounded!
Here,clearlyvisibleintheelectronmicrographs,seemstobeproofthatproteinimportintomitochondriaoccursduringtranslation.Howmightyoureconcilethisresultwiththeprevailingviewthatmitochondriaproteinsareimportedaftertheyhavebeensynthesizedandreleasedfromribosomes?
信号肽与膜受体结合,阻断剂阻止了新生肽的释放。
2006.11.21
1.Shortanswer:
Givethesignificance(notthedefinition)ofthefollowingtermsorphases.Saywhattheydoorwhytheyareimportant.e.g.endoplasmicreticulum:
delineatesanintracellularcompartmentthatfunctionsinthesortingofnewlysynthesize
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