ALEVEL期中复习.docx
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ALEVEL期中复习
Review
1.WhatisSA/V?
WhatisSA?
WhatisV?
PleasecalculatetheSA/Vofa3cm*3cmsquareanditsSA/Vwhenitwascutinto27littlesquareswith1cmofthesidelength?
SA/Visthesurfaceareatovolumeratio.SAissurfacearea.Visvolume.
theSA/Vofa3cm*3cmsquare=3*3*6/(3*3*3)=2
theSA/Vofa1cm*1cmsquare=1*1*6/(1*1*1)=6
2.Pleasecalculatethemagnificationofthisimage,andthereallengthoftheinsect’sbody.
32mm*1000/100um=32083mm/320*1000=259um
3.Wehavelearnedaboutthecelltheory,doyouknowwhatisit?
Areallofthethreeideasofthetheorycorrect?
Basedonyourunderstandingandpresentation,whodidgreatcontributiontothedevelopmentofmicroscopeandthistheory?
(Ifyoudonotknow,askyourclassmateswhodidthispresentation)Leewenhoek,RobertHooker,Schleiden,Schwann,RobertBrown,Virchow,doyouknowthem?
Whatdidtheyfoundout?
Themajorprinciplesofthecelltheoryarethefollowing:
1.Allorganismaremadeofcells.2.Allexistingcellsareproducedbyotherlivingcells.3.Thecellisthemostbasicunitoflife.
RobertBrown(21December1773–10June1858)wasaScottish(苏格兰)botanist(植物学家)and palaeobotanist(古植物学家)whomadeimportantcontributionstobotanylargelythroughhispioneeringuseofthemicroscope.Hiscontributionsincludeoneoftheearliestdetaileddescriptionsofthe cellnucleus and cytoplasmicstreaming;theobservationof Brownianmotion(布朗运动);earlyworkonplant pollination and fertilisation,includingbeingthefirsttorecognisethefundamentaldifferencebetween gymnosperms and angiosperms(裸子植物和被子植物);andsomeoftheearlieststudiesin palynology(孢粉学).Healsomadenumerouscontributionstoplanttaxonomy,includingtheerection(建立)ofanumberofplantfamiliesthatarestillacceptedtoday.
4.Whymanysmallcellsaremoreefficientthanonehugecell?
Isitbetterforacellassmallaspossible,ortheyneedtohaveapropersize?
Why?
Useexamplestotellmetheanswer.Ifyouarenotsure,askyourclassmatesdidthepresentation.
Thesizeofacellislimitedbyitsneedtoexchangematerialswithitsenvironment.Ifacellbecomestoolarge,itsdiffusiondistancebecomestoolongtobeefficientanditssurfaceareatovolumeratiobecomestoosmalltoallowthenecessaryexchange.However,itisnotbetterforacellassmallaspossible,becauseitmusthavenecessarycompositionsuchasnucleiandcytoplasm.
Forexample,SA/Vof1cmcubeis6butSA/Vof10cmcubeisonly0.6.Itmeansthevolumeincreasesmorerapidlythanthesurfaceareawhicheventuallycreatesaproblemforthecell.Waysofdealingwiththisaretoincreasethesurfaceareabyprotrudingextensions.Multicellularorganismsfacethesameproblem.Thisiswhy,forexample,wehavelungsandacircularsystem.
5.Pleaselistallthedifferencesbetweenprokaryoticandeukaryoticcells.
Prokaryotes
Eukaryotes
Diameterofcell
0.5-5um
40umandcommonly1000-10000timesthevolumeofprokaryotes
DNA
Circularandliesfreeinthecytoplasm.DNAisnaked.
Notcircularandiscontainedinanucleus.DNAisassociatedwithprotein,formingchromosomes.
Ribosomes
Smaller(18nmdiameter)
Larger(22nmdiameter)
ER
Notpresent
Present
Organelles
Veryfew
Manytypes
Cellwall
Present
Sometimespresent,e.g.Inplants
6.Pleaselistthedifferencesbetweenplantandanimalcells
Animalcells
Plantcells
nucleus
√
√
cytoplasm
√
√
Plasmamembrane
√
√
Endoplasmicreticulum
√
√
Golgiapparatus
√
√
ribosome
√
√
mitochondria
√
√
vacuole
√
√
Cellwall
×
√
chloroplast
×
√
centriole
√
×
Lysosome
√
√
√=present×=absent
7.IfIdrawa1mmeggin1cm,whatisthemagnitude?
Andiftheyolkoftheeggis0.5mm,whatwillbethesizeinmydrawing?
themagnitude=1cm/1mm=10.
thesizeoftheyolkinmydrawingshouldbe0.5mm*10=5mm.
8.Thecellmembrane,whatarethedifferentpartsinthemembrane?
Thehead?
Thetail?
Hydrophilic?
Hydrophobic?
Integralprotein?
Peripheralprotein?
Glycoprotein?
Cholesterol?
Theirfunctions?
Thecellmembraneconsistsofadoublelayerofphospholipidsinterspersedwithavarietyofothermolecules.Aphospholipidiscomposedofthreebasicparts:
achargedphosphategroup,glycerolandtwofattyacidchains.Together,theglycerolandthephosphategroupformthe“head”ofaphospholipid;thefattyacidchainsformthe“tail”.becausetheheadbearsacharge,itispolar.Recallthatwatermoleculesarealsopolar.Therefore,the“head”ishydrophilic.Incontrast,thefattyacidtailsarenonpolarandcannotformhydrogenbondswithwater.Asaresult,thenonpolartailsareattractedtoeachotherandrepelledbywater.
Othercomponents:
proteins(integral,peripheral,glycoprotein),cholesterol.
Integralprotein(内在蛋白、整合蛋白)actaschannelproteins.
Peripheralprotein(外在蛋白、周边蛋白)canactasreceptors,enzymes,antigensandcarriers.
Glycoprotein:
theycanactasreceptorsorantigens.
Cholesterol:
itcanregulatethefluidityandstabilityofthemembrane.
9.Couldyoutellmethethreetypesoftransportationthroughthecellmembrane?
Whataretheirnames?
Whatarethedifferencesamongthem?
Whatarethethreetypesofpassivetransportation?
Whichtransportationneedsenergy?
Whichonesneedproteintocarrythesubstance?
Whatarethedifferentfunctionsofproteinsinfacilitateddiffusionandactivetransportation?
Diffusion
osmosis
activetransport
Simplediffusion
Facilitateddiffusion
Energy
Noneed
Noneed
Noneed
need
Proteinchannel
Noneed
need
Noneed
need
Concentration
high→low
high→low
high→low
low→high
10.Whydosomeofthemoleculescangothroughcellmembranebysimplediffusion,butsomeothersneedtogobythehelpofsomeproteins?
Thinkaboutpolarityofthemolecules,sizeofthemolecules,andtheconcentrationgradient.
Nonpolarandsmallmoleculessuchaswatermolecules,oxygenmoleculesandglycerolcangothroughcellmembranefromhighconcentrationgradienttolowconcentrationgradientwithoutthehelpofsomeproteins.However,polarandsmallmoleculessuchasaminoacidandglucoseneedtogobythehelpofsomeproteins.TheygofromhighconcentrationgradienttolowconcentrationgradientbyFacilitateddiffusionorbyactivetransportincontrast.
11.Whatarethethreemajorstagsofacellcycle?
Whichstageisthelongestone?
Whichistheshortest?
Whichstageisresponsiblefornucleusdivisionandwhichoneisforcelldivision?
Whathappensineveryphaseofinterphase(G1,S,G2)andmitosis(thefourphases)?
Youneedtobeabletoeasilyidentifyeveryphasesandknowthethingshappensineveryphase.
Thecellcycleistheperiodbetweenonecelldivisionandthenext.Ithasthreephases,namelyinterphase,nucleardivisionandcelldivision.
①Interphase:
G1+S+G2=90%ofthecellcycle.
G1:
growth,proteinsynthesis,increaseinthenumberofmitochondriaand/orchloroplast.
S:
DNAreplication.
G2:
growth,proteinsynthesis,preparationformitosis/cytokinesis.
②nucleardivision:
prophase,metaphase,anaphaseandtelophase.
Prophase:
nucleus,nucleolusdisappear;mitoticspindleforms;prophaseisthelongestphaseofmitosis.
Metaphase:
sisterchromatidslineupatmiddle;centrosomesareatoppositepolesofthecells;spindlefibersrunfromthecentrosomestothekinetochoresinthecentromeres.
Anaphase:
sisterchromatidsaresplitapart;thisistheshortestphaseofmitosis.
Telophase:
nucleiofnewcellsreform;chromatinuncoils.
③celldivision:
inanimalcells,celldivisioninvolvesconstrictionofthecytoplasmbetweenthetwonewnuclei,aprocesscalledcytokinesis(胞质分裂).Inplantcellsitinvolvestheformationofanewcellwallbetweenthetwonewnuclei.
12.Whatarechromosome,chromatinandsisterchromatids?
Aretheysameincomposition?
Whataretheymadeof?
AchromosomeisonelongcontinuousthreadofDNAthatconsistsofnumerousgenesalongwithregulatoryinformation.Itistightlycondensed.IninterphaseDNAwrapsaroundhistonesloosely,whichiscalledchromatin.Asacellprogressesintomitosis,chromatinfurthercondenses.RecallthateachchromosomehasalreadybeencopiedduringthepreviousSstage.Thus,thechromosomelookssimilartoan“X”inwhichtheleftandrighthalvesaretwoidenticalDNAdoublehelixes.Onehalfofaduplicatedchromsomesiscalledachromatid.Together,thetwoidenticalchromatidsarecalledsisterchromatids.
13.Whatisstemcell?
Howdidyougrowfromasinglezygote?
Couldyoujusttellmethemajorprocesshappened,youmayneedtousethewordscelldivisionanddifferentiation.
Stemcellsareauniquetypeofbodycellthathavetheabilityto
(1)divideandrenewthemselvesforlongperiodsoftime,
(2)remainundifferentiatedinform,and(3)developintoavarietyofspecializedcelltypes.Whenastemcelldivides,itformseithertwostemcellsoronestemcellandonespecializedcell.
14.Iscelldivisionalwaysagoodthing?
Ifcelldivisionbecomeuncontrollable,whatdoesitmean?
Whatkindofillnesswillweget?
Cancersarecausedbyuncontrolledmitosis,possiblyastheresultofamutationinageneorgeneswhichcontrolcelldivision.Agentswhichcausecancerareknownascarcinogensandincludeionisingradiation,manychemicalsandviruses.Somecancershaveahereditarylink.
15.Ontheearth,morethan90%ofthesubstancesareorganicsubstances;couldyoutellmehowtodistinguishorganicsubstancesandinorganicones?
Pleasegivemeseveralexamplesoforganicsubstances.Whichelementisamustinorganicsubstances?
Carbonisoftencalledthebuildingblockoflifebecausecarbonatomsarethebasisofmostmoleculesthatmakeuplivingthings.Fourmaintypesofcarbon