一．Translation：（本大題共15分，每小題1.5分）1.Luxurygenes答案：奢侈基因2.Electrontransporter答案：電子傳遞體3.Gapjunction答案：間隙連接4.Telomerase答案：端粒酶5.Semi-autonomousorganelle答案：半自主性細胞器6.Targetcells答案：靶細胞7.F0-F1couplingfactor答案：F0-F1偶聯因子8.Primarylysosome答案：初級溶酶體9.Microtubule答案：微管10.Integrin答案：整聯蛋白二．Explanation：（本大題共55分，每小題5分）1.neuralstemcell(NSC)答案：存在于成體腦組織中的一種干細胞，它可生成神經元、星形膠質細胞、少突膠質細胞。亦可轉分化成血細胞和骨骼肌細胞。2.XinactivationX答案：雌性成體細胞中兩條X染色體中的一條處于正常失活狀態。3.cellline細胞系答案：在培養中由原代培養物產生的可無限增殖的細胞群。一般為腫瘤細胞或轉化細胞形成。4.polymorphicnucleus多形核答案：哺乳動物顆粒白細胞中形狀不規則的核。5.voltage-gatedionchannel電壓門控通道答案：興奮細胞質膜上的一種離子通道，對跨膜電位差的變化極為敏感，因膜電位達到一定閾值而開放。6.contractileprotein收縮蛋白答案：細胞中參與收縮過程的蛋白質，如肌動蛋白和肌球蛋白。7.cellcoat答案：又稱糖萼（glycocalyx），動物細胞質膜外的一層黏多糖物質，以共價鍵和膜蛋白或膜脂結合形成糖蛋白或糖脂，它對膜蛋白有保護作用，并在分子識別中起重要作用8.λ-phagevectorλ-噬菌體載體：答案：由λ噬菌體DNA發展而來的DNA克隆載體9.adaptorprotein銜接器蛋白答案：在細胞內信號傳遞途徑中，凡是在不同蛋白質間起連接作用的蛋白質的通稱。10.celladhesion細胞黏附答案：動物細胞通過細胞表面的黏附分子介導細胞之間或細胞與細胞外基質之間的黏附。11.lamin核纖層蛋白答案：核纖層結構的組成成分，屬于中間纖維蛋白家族；核纖層蛋白隨著細胞分裂發生周期性的磷酸化與去磷酸化變化，某些核纖層蛋白在體外能夠自我組裝成10nm的纖維。三．Answerquestions：（本大題共30分，每小題10分）1.Whywesaythattheorganellesofendoplamicmembraneisaunitedwhole？答:從功能上看,細胞內膜結合細胞器的分布是功能越重要越靠近中央;從層次看,上游的靠內,下游的靠外。如細胞核位于細胞的中央,它是細胞中最重要的細胞器,有兩層膜結構。細胞核的外膜與內質網的膜是聯系在一起的,細胞核的外膜是粗面內質網的一部分。粗面內質網的功能是參與蛋白質合成,其作用僅次于細胞核,所以內質網位于細胞核的外側。高爾基體在內質網的外側,接受來自內質網的蛋白質和脂肪,然后對它們進行修飾和分選,它所完成的是內質網的下游工作。溶酶體是含有水解酶的囊泡,它是由高爾基體分泌而來。內體是由內吞作用產生的具有分選作用的細胞器,它能向溶酶體傳遞從細胞外攝取的物質,這種細胞器一般位于細胞質的外側。另外還有線粒體、過氧化物酶體等分布在細胞的不同部位。如果是植物細胞還有葉綠體和中央大液泡,它們是按功能定位。造成內膜系統的動態特性主要是由細胞中三種不同的生化活動引起的:①蛋白質和脂的合成活動:在動物細胞中主要涉及分泌性蛋白的合成和脂的合成和加工。脂的合成在光面內質網,而分泌蛋白的合成起始于粗面內質網,完成于高爾基體。②分泌活動:③內吞活動(endocytosispathway),是分泌的相反過程,細胞將細胞外的物質吞進內體和溶酶體。2.Whatiscelldifferentiation？Pleaseintroducethemechanism.答：1.細胞分裂的不對稱性：在細胞分裂時一些重要的分子被不均等地分配到兩個子細胞中2.細胞間的相互作用：（1）胚胎誘導(embryonicinduction):胚胎發育過程中,一部分細胞影響相鄰細胞向一定方向分化的作用.進一步更復雜的模式由細胞間相互作用產生誘導的相互作用可以在原本等同的細胞中建立起有序的差異；（2）分化抑制:分化成熟的細胞可以產生抑素,抑制相鄰細胞發生同樣的分化；（3）細胞數量效應；（4）細胞外基質的影響；（5）激素的作用3.染色體與細胞分化：（1）染色體結構的變化；（2）基因刪除:原生動物,昆蟲,甲殼動物；（3）基因擴增:果蠅多線染色體；（4）基因重排:免疫球蛋白基因(106~108種抗體)；（5）DNA的甲基化與異染色質化:胞嘧啶的甲基化使基因失活.4,基因與細胞分化無論是母體mRNA的作用還是細胞間的相互作用,其結果是啟動特定基因的表達.母體基因→間隙基因→成對基因→體節極性基因→同源異形基因(homeoticgene,Hox)5.奢侈基因與管家基因生物體細胞中含有決定生長分裂和分化的全部基因信息，按其與細胞分化的關系，可將這些基因分為兩大類:奢侈基因和管家基因。奢侈基因(luxurygene)：編碼細胞特異性蛋白，與各種分化細胞的特定性狀直接相關，這類基因對細胞自身生存無直接影響。管家基因(housekeepinggene)：這類基因的表達產物為細胞生命活動持續需要和必不少，但與細胞分化的關系不大，在細胞分化中只起協助作用。從分子層次看，細胞分化主要是奢侈基因中某種(或某些)特定基因選擇性表達的結果。某些基因的選擇性表達合成了執行特定功能的蛋白質，從而產生特定的分化細胞類型。3.Pleasenarratetherelationshipofoncogeneandtumer-suppressorgene.癌基因是控制細胞生長和分裂的正常基因的一種突變形式，能引起正常細胞癌變。二抑癌基因實際上是正常細胞增殖過程中的負調控因子，它編碼的蛋白往往在細胞周期的檢驗點上起阻止周期進程的作用。如果抑癌基因突變，喪失其對細胞增殖的負調控作用，則導致細胞周期失控而過度增殖。由抑癌基因編碼的蛋白能夠結合到原癌基因的啟動子或增強子等位點，使轉錄復合物不能結合到這些位點，從而不能完成轉錄和翻譯，失去了對細胞周期的促進作用。通過癌基因和抑癌基因的協同作用，共同調控細胞的正常的增殖過程。一．Translation：（本大題共15分，每小題1.5分）1.Gatedchannel答案：門通道2.Targetcells答案：靶細胞3.Determinants答案：決定子4.EScells答案：胚胎干細胞5.Channelprotein答案：通道蛋白6.actinfilaments答案：肌動蛋白絲7.Dedifferentiation答案：脫(去)分化8.Stemcells答案：干細胞9.Molecularchaperone答案：分子伴侶10.G-protein答案：G蛋白二．Explanation：（本大題共55分，每小題5分）1.thickfilament粗（肌）絲答案：橫紋肌中的肌球蛋白II絲，直徑約12－14nm。2.laserscanningconfocalmicroscope答案：利用細激光束通過物鏡掃描標本成像,將不同光切面的影像經計算機圖象處理，獲得三維影像。3.ultrastructure超微結構答案：細胞從亞顯微水平到分子水平的結構的統稱，亦稱亞顯微結構（submicroscopicstructure）。4.liposome脂質體用懸浮在水中的磷脂分子人工制備成的脂雙層小膜泡。5.transdifferentiation轉分化答案：(1)已分化細胞經去分化后再分化成另一種細胞的現象，如色素細胞分化成晶狀體。(2)一種組織的干細胞能夠分化成他種組織細胞的現象。6.dockingprotein停泊蛋白答案：內質網膜上的信號識別顆粒受體。7.thylakoid類囊體答案：葉綠體基質中由單位膜封閉形成的扁平囊。8.nuclearporecomplex核孔復合體答案：核被膜上溝通核質和細胞質的復雜隧道結構，由多種核孔蛋白構成。隧道的內、外口和中央有由核糖核蛋白組成的顆粒。核孔對進出核的物質有控制作用。9.cytoplast,cytosome胞質體答案：利用物理或化學方法，將細胞核去除后所得到的細胞部分，可以用來研究細胞核與細胞質的關系10．axonaltransport細胞器或分子沿神經細胞軸突定向的運輸，可以是順向的（從細胞體向外）或逆向的（向著細胞體11.sexdetermination性別決定答案：由于性染色體上的性別決定基因地活動，胚胎發生了雄性和雌性的性別差異。在哺乳動物中，基因型若為XY，則為雄性性，XX為雌性。三．簡答題：（本大題共30分，每小題10分）1.Pleasenarratethecharacteristicsoftheagingcell.答案：1，水份減少，代謝速率減慢2，呼吸速率降低3，酶溶性下降4，色素，鈣以及一些惰性物積累，不溶性廢物增加5膠原彈性降低，張力增強。分子鏈間的2.Pleaseintroducethemaincheckpointsduringthecellcycle.答：細胞周期檢驗點是細胞周期調控的一種機制,主要是確保周期每一時相事件的有序、全部完成并與外界環境因素相聯系。它保證前一個事件完成之后，才啟動下一個事件。主要檢驗點包括：G1/S檢驗點：在酵母中稱start點，在哺乳動物中稱R點(restrictionpoint)，控制細胞由靜止狀態的G1進入DNA合成期，相關的事件包括：DNA是否損傷？細胞外環境是否適宜？細胞體積是否足夠大？S期檢驗點：DNA復制是否完成？G2/M檢驗點：是決定細胞一分為二的控制點，相關的事件包括：DNA是否損傷？細胞體積是否足夠大？紡錘體組裝檢驗點：任何一個著絲點沒有正確連接到紡錘體上，引起細胞周期中斷。3.Whatisthebasiccharacteristicsofcancercells?1.細胞生長與分裂失去控制：癌細胞的生長與分裂失去控制，成為不死的永生細胞核質比例增大，分裂速度加快，結果破壞了正常組織的結構與功能。2.具有侵潤性和擴散性：癌細胞粘著性下降，具有侵潤性和擴散性，易于浸潤周圍的健康組織，或通過血液循環或通過淋巴途徑轉移并在其它部位粘著和增殖。3.細胞間相互作用改變：正常細胞通過細胞表面特異性蛋白的相互作用識別，進而形成特定的組織與器官。癌細胞沖破了細胞識別作用的束縛，異常表達某些膜受體蛋白，以便與別處細胞粘著生長。4.蛋白表達譜系或蛋白活性改變：出現一些錯位表達的蛋白，具有較高的端粒酶活性，異常表達與惡性增殖、擴散等過程相關的蛋白。5.mRNA轉錄譜系的改變：基因表達和調控方向的改變。體外培養的惡性轉化細胞的特征：人工誘導培養的惡性轉化細胞同樣具有無限增殖的能力，貼壁性下降，失去運動和分裂的接觸抑制一．中英互譯：（本大題共30分，每小條1分）1.Gatedchannel答案：門通道2.Discontinuoussecretion答案：不連續分泌3.Targetcells答案：靶細胞4.Triggerprotein答案：觸發蛋白5.generaltranscriptionfactors答案：通用轉錄因子6.Determinants答案：決定子7.Celldifferentiation答案：細胞分化8.N-linkedoligosaccharides答案：N-連接寡糖9.Germplasm答案：生殖質10.Peroxisome答案：過氧化物酶體11.EScells答案：胚胎干細胞12.Myeloidbody答案：髓樣小體13.Coatedvesicle答案：有被小泡14.Channelprotein答案：通道蛋白15.actinfilaments答案：肌動蛋白絲16.calmodulin答案：鈣調蛋白（鈣調素）17.Informasomes答案：信息體18.Spliceosome答案：剪接體19.Dedifferentiation答案：脫(去)分化20.Proto-oncogenes答案：原癌基因21.Dictyosome答案：分散高爾基體22.Stemcells答案：干細胞23.Molecularchaperone答案：分子伴侶24.G-protein答案：G蛋白25.Carrierprotein答案：載體蛋白(透性酶)26.Membranedifferentiation答案：膜分化27.Oncogene答案：癌基因28.Ribozyme答案：RNA催化劑(核酶)29.Alternativesplicing答案：交替剪接30.Lysosomalmembraneglycoprotein答案：溶酶體膜糖蛋白二．名詞解釋：（本大題共30分，每小條2分）1.thickfilament粗（肌）絲答案：橫紋肌中的肌球蛋白II絲，直徑約12－14nm。2.osteoclast破骨細胞答案：在生長中的骨的骨髓中形成的一種巨大的多核細胞，具有破骨功能。osteocyte骨細胞3.ultrastructure超微結構答案：細胞從亞顯微水平到分子水平的結構的統稱，亦稱亞顯微結構（submicroscopicstructure）。4.fusin引信蛋白答案：在各種CD4細胞中廣泛表達的一種7次穿膜的G蛋白，與趨化因子受體相連，當HIV病毒感染T細胞時起輔因子的作用。5.glialcells膠質細胞答案：神經系統中的支持細胞，包括脊椎動物中樞神經系統中的少突膠質細胞和星形膠質細胞以及周圍神經系統中的雪旺細胞。6.dockingprotein停泊蛋白答案：內質網膜上的信號識別顆粒受體。7.lamellipodium片足答案：細胞表面的外被質膜的薄片狀突起，內部有肌動蛋白絲網絡的支撐，與細胞運動有關。8.myofibril肌原纖維答案：由粗肌絲和細肌絲規則排列構成的肌纖維亞單位。9.cytoplast,cytosome胞質體答案：利用物理或化學方法，將細胞核去除后所得到的細胞部分，可以用來研究細胞核與細胞質的關系。10.axonaltransport軸突運輸答案：細胞器或分子沿神經細胞軸突定向的運輸，可以是順向的（從細胞體向外）或逆向的（向著細胞體）。11.contractileprotein收縮蛋白答案：細胞中參與收縮過程的蛋白質，如肌動蛋白和肌球蛋白。12.Vitalstaining,intravitalstaining活體染色答案：使用毒性小的染料對活體細胞或組織的染色。13.Barrbody巴（爾）氏小體答案：雌性哺乳動物體細胞在有絲分裂間期的細胞核中染色很深、由一條失活的X染色體凝縮而成的染色質小體，又稱性染色質小體(sex-chromatinbody)；1949年為M.Barr所發現。14.monoclonalantibody單克隆抗體答案：從某一雜交瘤克隆中分泌的抗體。因為每一個克隆都來自于一個B細胞，因此制備的抗體具有高度專一性。15.leucoplast白色體答案：一種無色的質體。三．簡答題：（本大題共40分，每小條8分）1.細胞分化是被選定的不同特異基因表達的結果，請舉例說明分化時特異基因的表達調控方式2.簡述衰老細胞的特征。答案：1，水份減少，代謝速率減慢2，呼吸速率降低3，酶溶性下降4，色素，鈣以及一些惰性物積累，不溶性廢物增加5膠原彈性降低，張力增強。分子鏈間的3.高爾基體在形態結構上至少由互相聯系的三個部分組成，請簡述各部分的功能。答案：1，高爾基體順面膜囊中間多孔而且連續分支狀的網結構，接受來自內質網新合成的物質并將其分類后大部分轉入高爾基體中間膜囊，小部分蛋白質與脂質再返回內質網；2， 高爾基體中間膜囊多為糖基化修飾、糖脂的形成以及與高爾基體有關的多糖的合成的場所；3， 高爾基體反面膜囊參與蛋白質的分類與包裝最后由高爾基體輸出。功能：合成糖類；將內質網合成的多種蛋白質進行加工分類包裝并運送到特定部位或分泌到細胞外；蛋白質的糖基化作用和其修飾；通過蛋白酶水解作用使其成為活性肽；其它加工過程成為活性肽。4.請詳述細胞質膜的分子結構及其基本特性5.核糖體各活性部位及其在蛋白質合成過程中的作用是什么？一：Giveagoodexplanationtothewordslistedbelow.1,primaryculture：Thecellsareobtaineddirectlyfromtheorganism.Mostprimaryculturesofanimalcellsareobtainedfromembryos,whosetissuesaremorereadilydissociatedintosinglecellsthanthoseofadults.Dissociationisaccomplishedwiththeaidofaproteolyticenzyme,suchastrypsin.Thetissueisthenwashedfreeoftheenzymeandusuallysuspendedinliquidmediatostartacellculture.2,liposome:Aimportantfeatureofthelipidbilayerisitsabilitytoselfassemble,forexample,asmallamountofphosphatidylcholineisdispersedinanaqueoussolution,thephospholipidmoleculesassemblespontaneouslytoformthewallsoffluid-filledsphericalvesicles,calledliposomes.3,basementmembrane:Acontinuoussheetthat(1)surroundsmuscleandfatcells,(2)underliesthebasalsurfaceofepithelialtissues,suchastheepidermisoftheskin,(3)underliestheinnerendothelialliningofbloodvessels.Basementmembranesprovidemechanicalsupportfortheattachedcells,generatesignalsthatmaintaincellsurevival,serveasasubstratumforcellmigration,separateadjacenttissueswithinanorgan,andactasabarriertothepassageofmacromolecules.4,Fibronectin:Consistsofalineararrayofdistinct“buildingblocks”thatgiveseachpolypeptideoftheextracellularmatrixamodularconstruction.Eachfibronectinpolypeptideisconstructedfromasequenceofapproximately30independentlyfoldingFnmoidules,whileFn-typemoduleswerefirstdiscoveredinfibronectin,theyarefoundaspartofmanyotherproteins,rangingfrombloodclottingfactorstomembranereceptorsandotherproteinsoftheECM.Eachofthetwopolypeptidechainsthatmakeupafibronectinmoleculecontains(1)BindingsitesforothercomponentsoftheECM,suchascollagensandproteoglycans.(2)Bindingsitesforreceptorsonthecellsurface.5,junctionalcomplex:Thecellsofcertaintissues,particularlyepitheliaandcardiacmuscle,arenotoriouslydifficulttoseparatefromoneanotherbecausetheyareheldtogethertightlybyspecializedcalcium-dependentadhesivejunctions.Therearetwomaintypesofadhesivejunctions:adherensjunctionsanddesmosomes.Inadditiontoadhesivejunctions,epithelialcellsoftencontainothertypesofcelljunctionsthatarealsolocatedtheirlateralsurfacesneartheapicallumen.Whenthesejunctionsarearrangedinaspecificarray,thisassortmentofsurfacespecializationsiscalledajunctionalcomplex.6,gapiunction:Gapjunctionsaresitesbetweenanimalcellsthatarespecializedforintercellularcommunication.Theplasmamembranesofadjacentcellscomeveryclosetooneanotherbutdonotmakedirectcontact.Instead,thecleftbetweenthecllsisspannedbyveryfinestrandsthatarecomposedentirelyofanintegralmembraneproteincalledconnexin.Eachconnexoniscomposedofsixconnexinsubunitsarrangedaroundacentralopening.Gapjunctionscanputalargenumberofcellsofatissueintointimatecytoplasmiccontact.Thishasimportantphysiologicconsequences,becauseanumberofhighlyactiveregulatorysubstances,suchascAMPandinositolphosphates,aresmallenoughtofitthroughgap-junctionchannels.Asaresult,gapjunctionshavethepotentialtointegratetheactivitiesofindividualcellsofatissueintofunctionalunit.一：Giveagoodexplanationtothewordslistedbelow.(5x8=40points)1,cellline：Normal(nonmalignant)cellscandividealimitednumberoftimes(typically50to100)beforetheyundergosenescenceanddeath.Becauseofthis,manyofthecellsthatarecommonlyusedintissueculturestudieshaveundergonegeneticmodificationsthatallowthemtobegrownindefinitely.Cellsofthistypearereferredtoasacellline.2,Laminin：Lamininsareafamilyofextracellularglycoproteinsthatconsistofthreedifferentpolypeptidechainslinkedbydisulfidebondsandorganizedfintoamoleculeresemblingacrosswiththreeshortarmsandonelongarm.Atleast15differentlamininshavebeenidentified.Likefibronectin,extracellularlamininscangreatlyinfluenceacell’spotencialformigration,growth,anddifferentiation.Forexample,lamininsplayacriticalroleinthemigrationofprimordialgermcells.Thesecellsariseintheyolksac,whichislocatedtheembryoitself,andthenmigratebywayofthebloodstreamandembryonictothedevelopinggond,wheretheyeventuallygiverisetospermoreggs.Duringtheirmigration,theprimordialgermcellstraversesurfacesthatareparticularlyrichinlaminin.Studiesindicatethattheprimordialgermcellspossessacell-surfeceproteinthatadheresstronglytooneofthesubunitsofthelamininmolecule.3,Cadherins：ThecadherinsarealargefamilyofglycoproteinsthatmediateCa2+-dependentcell-celladhesionandtransmitsignalsfromtheECMtothecytoplasm.Cadherinsjoincellsofsimilartypetooneanotheranddosopredominantlybybindingtothesamecadherinpresentonthesurfaceoftheneighboringcell.Cadherinsarefoundonthesurfacesofmanydifferentcelltypesinanimals,witheachparticularmemberofthecadherinfamilyhavingaspecificdistributionwithinthebody.4,apoptosis：isaformofprogrammedcelldeathinmulticellularorganisms.Itisoneofthemaintypesofprogrammedcelldeaths(PCD)andinvolvesaseriesofbiochemicaleventsleadingtoacharacteristiccellmorphologyanddeath,inmorespecificterms,aseriesofbiochemicaleventsthatleadtoavarietyofmorphologicalchanges,includingblebbing,changestothecellmembranesuchaslossofmembraneasymmetryandattachment,cellshrinkage,nuclearfragmentation,chromatincondensation,andchromosomalDNAfragmentation.5,extracellularmessengermolecules：Cellsusuallycommunicatewitheachotherthroughextracellularmessengermolecules.Cellsignalingisinitiatedwiththereleaseofamessengermoleculebyacellthatisengagedinsendingmessagestoothercellsinthebody.Insomecases,themessengermoleculeneedonlydiffuseacrossanarrowcleftorthroughatinybloodvesselbeforethemessagerisreceivedbyanappropriatetargetcell.Inothercases,themessengermoleculemayhavetocirculatethroughtheentirebodybeforeitreachesspecifictargetcells.Cellscanonlyrespondtoanextracellularmessageiftheyexpressreceptorsthatspecificallyrecognizeandbindthatparticularmessengermolecule.6,chromatin:ChromatinistheDNA/protein/RNAcomplexextractedfromeukaryoticlysedinterphasenuclei.Themajorproteinsinvolvedinchromatinarehistoneproteins.AndthefunctionsofchromatinaretopackageDNAintoasmallervolumetofitinthecell,tostrengthentheDNAtoallowmitosisandmeiosis,andtoserveasamechanismtocontrolexpression.Changesinchromatinstructureareaffectedmainlybymethylation(DNAandproteins)andacetylation(proteins).ChromatinstructureisalsorelevanttoDNAreplicationandDNArepair.7，house-keepinggene:Expressedinallcelltypes,essentialforallcells,responsiblefortheroutinmetabolicfunctions.8，Hayflicklimit:isthenumberoftimesacellwilldividebeforeitstopsduetothetelomerereachingacriticallength.ItwasdiscoveredbyLeonardHayflickin1965,whenHayflickdemonstratedthatnormalhumancellsinacellculturedivideabout52timesbeforeenteringasenescencephase(refutingthecontentionbyAlexisCarrelthatnormalcellsareimmortal).EachmitosisshortensthetelomereappendixontheDNAofthecell,thustickingbackan"innerclock"foreachsubsequentcopyofthecell.Thismechanismisbelievedtohaveevolvedprimarilytoprotectthebodyfromcreatingapotentially-cancerouscell.BecauseofthefragmentedwayDNAreplicates,averyshorttelomeredcellmayleadtogenomicinstabilitywhentheproteinsmeanttobelocatedonthetelomerewillfailtoattachanditwillbemarkedasadouble-strandDNAbreak,possiblyleadingtocancer.三：Answerthefollowingquestions.((10x4=40points)1,Introducethetypeandfunctionofthecytoskeleton.Thecytoskeletonisacellular"scaffolding"or"skeleton"containedwithinthecytoplasm.Thecytoskeletonispresentinallcells;Itisadynamicstructurethatmaintainscellshape,oftenprotectsthecell,enablescellularmotion(usingstructuressuchasflagella,ciliaandlamellipodia),andplaysimportantrolesinbothintracellulartransport(themovementofvesiclesandorganelles,forexample)andcellulardivision.Actinfilaments/Microfilaments:Around7nmindiameter,thisfilamentiscomposedoftwointertwinedactinchains.Microfilamentsaremostconcentratedjustbeneaththecellmembrane,andareresponsibleforresistingtensionandmaintainingcellularshape,formingcytoplasmaticprotuberances(likepseudopodiaandmicrovilli-althoughthesebydifferentmechanisms),andparticipationinsomecell-to-cellorcell-to-matrixjunctions.Inassociationwiththeselatterroles,microfilamentsareessentialtotransduction.Theyarealsoimportantforcytokinesis(specifically,formationofthecleavagefurrow)and,alongwithmyosin,muscularcontraction.Actin/Myosininteractionsalsohelpproducecytoplasmicstreaminginmostcells.Intermediatefilaments:Thesefilaments,8to12nanometersindiameter,aremorestable(stronglybound)thanactinfilaments,andheterogeneousconstituentsofthecytoskeleton.Likeactinfilaments,theyfunctioninthemaintenanceofcell-shapebybearingtension(microtubules,bycontrast,resistcompression.Itmaybeusefultothinkofmicro-andintermediatefilamentsascables,andofmicrotubulesascellularsupportbeams).Intermediatefilamentsorganizetheinternaltridimensionalstructureofthecell,anchoringorganellesandservingasstructuralcomponentsofthenuclearlaminaandsarcomeres.Theyalsoparticipateinsomecell-cellandcell-matrixjunctions.Microtubules:Microtubulesarehollowcylindersabout25nmindiameter(lumen=approximately15nmindiameter),mostcommonlycomprisedof13protofilamentswhich,inturn,arepolymersofalphaandbetatubulin.Theyhaveaverydynamicbehaviour,bindingGTPforpolymerization.Theyarecommonlyorganizedbythecentrosome.3,Introducethephasesandfeaturesofmeiosis.Meiosisisaprocessofreductiondivisioninwhichthenumberofchromosomespercelliscutinhalf.Inanimals,meiosisalwaysresultsintheformationofgametes.Unlikethesingle-celldivisionofmitosis,meiosisinvolvestwocellulardivisions:meiosisIandmeiosisII.MeiosisIMeiosisIisquitesimilartomitosis.However,thereareanumberofcrucialdifferencesbetweenmeiosisIandmitosis,allofwhichwillbeoutlinedinthediscussionofeachindividualstagebelow.InterphaseI,Justasinmitosis,thecellundergoesDNAreplicationduringthisintermediatephase.Afterreplication,thecellhasatotalof46chromosomes,eachmadeupoftwosisterchromatidsjoinedbyacentromere.ProphaseI,chromosomeslineupalongthespindleinhomologouspairs.Then,inaprocesscalledsynapsis,thehomologouspairsactuallyjointogetherandintertwine,formingatetrad(twochromosomesoftwochromatidseach,orfourtotalchromatids).OftenthisintertwiningleadsthechromatidsofhomologouschromosomestoactuallyexchangecorrespondingpiecesofDNA,aprocesscalledcrossing-overorgeneticreassortment.AfterprophaseI,themeioticcellentersmetaphaseI.Duringthisphase,thenuclearmembranebreaksdown,allowingmicrotubulesaccesstothechromosomes.Stilljoinedattheircrossoverregionsintetrads,thehomologouspairsofchromosomes,withonematernalandonepaternalchromosomeineachpair,alignatthecenterofthecellviamicrotubules,asinmitoticmetaphase.Thepairsaligninrandomorder.DuringanaphaseI,thecentromeresdonotsplit:theentirematernalchromosomeofahomologouspairispulledtooneend,andthepaternalchromosomeispulledtotheotherend.DuringtelophaseI,thechromosomesarriveatseparatepolesanddecondense.Nuclearmembranesre-formaroundthem.Thecellphysicallydivides,asinmitoticcytokinesis.ThecellsproducedbymeiosisIquicklyentermeiosisII.ThesecellsdonotundergoDNAreplicationbeforeenteringmeiosisII.DuringmeiosisII,chromosomesalignatthecenterofthecellinmetaphaseIIexactlythewaytheydoinmitoticmetaphase.InanaphaseII,thesisterchromatidsseparate,onceagaininthesamefashionasoccursinmitoticanaphase.TheonlydifferenceisthatsincetherewasnosecondroundofDNAreplication;onlyonesetofchromosomesexists.WhenthetwocellssplitattheendofmeioisisII,theresultisfourhaploidcells.4,Thetypeandcharteristicsofcelljunctions.Occludingjunctions(tightjunctions)Anchoringjunctionsa.actinfilamentattachmentsitesi.cell-celladherensjunctions(e.g.,adhesionbelts)ii.cell-matrixadherensjunctions(e.g.,focalcontacts)b.intermediatefilamentattachmentsitesi.cell-cell(desmosomes)ii.cell-matrix(hemidesmosomes)Communicatingjunctionsa.gapjunctionsb.chemicalsynapsesc.plasmodesmata(plantsonly)5,WhatarethestepsofsignaltransductionbyG-proteinCoupledreceptors?HeterotrimericGproteinsarereferredtoasGproteinsbecausetheybindguaninenucleotides,eitherGDPorGTP.Allofthemconsistofthreedifferentpolypeptidesubunits,calledα,β,andγ.Thispropertydistinguishesthemfromsmall,monomericGproteins,suchasRas.HeterotrimericGproteinsareheldattheplasmamembranebylipidchainsthatarecovalentlyattachedtotheαandγsubunits.Theguaninenucleotide-bindingsiteispresentontheGαsubunit.ReplacementofGDPbyGTP,followinginteractionwithanactivedGprotein-coupledreceptors(GPCR),resultsinaconformationalchangeintheGαsubunit.Init’sGTP-boundconformation,theGαsubunithasalowaffinityofGβ，γ，leadingtoitsdissociationfromthecomplex.EachdissociatedGαSubunit(withGTPattached)isfreetoactivateaneffectorprotein,suchasadenylylcyclase.Inthiscase,activationoftheeffectorleadstotheproductionofthesecondmessengercAMP,OthereffectorsincludephospholipaseC-βandcyclicGMPphosphodiesterase.Secondmessengers,inturn,activeoneormorecellularsignalingproteins.一：Giveagoodexplanationtothewordslistedbelow.(4x10=40points)1,primaryculture:Thecellsareobtaineddirectlyfromtheorganism.Mostprimaryculturesofanimalcellsareobtainedfromembryos,whosetissuesaremorereadilydissociatedintosinglecellsthanthoseofadults.Dissociationisaccomplishedwiththeaidofaproteolyticenzyme,suchastrypsin.Thetissueisthenwashedfreeoftheenzymeandusuallysuspendedinliquidmediatostartacellculture.2,liposome:Aimportantfeatureofthelipidbilayerisitsabilitytoselfassemble,forexample,asmallamountofphosphatidylcholineisdispersedinanaqueoussolution,thephospholipidmoleculesassemblespontaneouslytoformthewallsoffluid-filledsphericalvesicles,calledliposomes.3,celldifferentiation:Adevelopmentalprocessinwhichstructuresandfunctionsbecomeincreasinglyspecialized.4,gapiunction:Gapjunctionsaresitesbetweenanimalcellsthatarespecializedforintercellularcommunication.Theplasmamembranesofadjacentcellscomeveryclosetooneanotherbutdonotmakedirectcontact.Instead,thecleftbetweenthecllsisspannedbyveryfinestrandsthatarecomposedentirelyofanintegralmembraneproteincalledconnexin.Eachconnexoniscomposedofsixconnexinsubunitsarrangedaroundacentralopening.Gapjunctionscanputalargenumberofcellsofatissueintointimatecytoplasmiccontact.Thishasimportantphysiologicconsequences,becauseanumberofhighlyactiveregulatorysubstances,suchascAMPandinositolphosphates,aresmallenoughtofitthroughgap-junctionchannels.Asaresult,gapjunctionshavethepotentialtointegratetheactivitiesofindividualcellsofatissueintofunctionalunit.5,chromosome:ChromosomesareorganizedstructuresofDNAandproteinsthatarefoundincells.AchromosomeisasingularpieceofDNA,whichcontainsmanygenes,regulatoryelementsandothernucleotidesequences.ChromosomesalsocontainDNA-boundproteins,whichservetopackagetheDNAandcontrolitsfunctions.Ineukaryotes,nuclearchromosomesarepackagedbyproteinsintoacondensedstructurecalledchromatin.ThisallowstheverylongDNAmoleculestofitintothecellnucleus.Thestructureofchromosomesandchromatinvariesthroughthecellcycle.6,nucleosome:arethefundamentalrepeatingunitsofeukaryoticchromatin,TheyarethesmalleststructuralunitofeukaryoticDNApackaging,fundamentaltothestructureofthechromosome(s)insidethecellnucleusandcanplayaroleincontrollinggeneexpression.Theyaremadeupofabout146basepairsofDNAandfourpairsofproteinscalledhistones,andresemble"beadsonastringofDNA"whenobservedwithanelectronmicroscope(a10nmfiber).Theproteinsthatmakeupthenucleosomearecalledhistones.HistonesH2A,H2B,H3andH4formthecoreofthenucleosome,aroundwhichtheDNAiswrapped,whilehistoneH1sitsonthebaseofthenucleosomeatthejunctionbetweennucleosomeDNAandlinkerDNA,extendingalongtheDNAintothelinkerregion.7,luxurygene:Tissue-specificgenes,expressedinspecialcells,makingonecelltypedifferentfromanothercelltype.8,cellcycle:Thecellcycle,orcell-divisioncycle,istheseriesofeventsthattakeplaceinaeukaryoticcellleadingtoitsreplication.Theseeventscanbedividedintwobriefperiods:interphase—duringwhichthecellgrows,accumulatingnutrientsneededformitosisandduplicatingitsDNA—andthemitotic(M)phase,duringwhichthecellsplitsitselfintotwodistinctcells,oftencalled"daughtercells".Thecell-divisioncycleisavitalprocessbywhichasingle-celledfertilizedeggdevelopsintoamatureorganism,aswellastheprocessbywhichhair,skin,bloodcells,andsomeinternalorgansarerenewed.三：Answerthefollowingquestions.(10x4=40points)1,what’sthestructureandfunctionofsERandrER?TheendoplasmicreticulumorERisanorganellefoundinalleukaryoticcells.ERiscalledsarcoplasmicreticuluminstraitedmuscle.Itispartoftheendomembranesystem.TheERmodifiesproteins,makesmacromolecules,andtransferssubstancesthroughoutthecell.ProkaryoticorganismsdonothavemembranousorganellesandthusdonothaveanER.ThebasicstructureandcompositionoftheERissimilartotheplasmamembrane,althoughitisactuallyanextensionofthenuclearmembrane.TheERisthesiteofthetranslation,folding,andtransportofproteinsthataretobecomepartofthecellmembrane(e.g.,transmembranereceptorsandotherintegralmembraneproteins)aswellasproteinsthataretobesecretedor"exocytosed"fromthecell.PartsoftheERarecoveredwithribosomes(whichassembleaminoacidsintoproteins