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(lián)因子8.Primarylysosome答案：初級溶酶體9.Microtubule答案：微管10.Integrin答案：整聯(lián)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(jīng)元、星形膠質(zhì)細胞、少突膠質(zhì)細胞。亦可轉(zhuǎn)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(tài)。3.cellline細胞系答案：在培養(yǎng)中由原代培養(yǎng)物產(chǎn)生的可無限增殖的細胞群。一般為腫瘤細胞或轉(zhuǎn)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(guī)則的核。5.voltage-gatedionchannel電壓門控通道答案：興奮細胞質(zhì)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(zhì)，如肌動蛋白和肌球蛋白。7.cellcoat答案：又稱糖萼（glycocalyx），動物細胞質(zhì)膜外的一層黏多糖物質(zhì)，以共價鍵和膜蛋白或膜脂結(jié)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(fā)展而來的DNA克隆載體9.adaptorprotein銜接器蛋白答案：在細胞內(nèi)信號傳遞途徑中，凡是在不同蛋白質(zhì)間起連接作用的蛋白質(zhì)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(dǎo)細胞之間或細胞與細胞外基質(zhì)之間的黏附。11.lamin核纖層蛋白答案：核纖層結(jié)構(gòu)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(fā)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(nèi)膜結(jié)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(nèi),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(jié)構(gòu)。細胞核的外膜與內(nèi)質(zhì)網(wǎng)的膜是聯(lián)系在一起的,細胞核的外膜是粗面內(nèi)質(zhì)網(wǎng)的一部分。粗面內(nèi)質(zhì)網(wǎng)的功能是參與蛋白質(zhì)合成,其作用僅次于細胞核,所以內(nèi)質(zhì)網(wǎng)位于細胞核的外側(cè)。高爾基體在內(nèi)質(zhì)網(wǎng)的外側(cè),接受來自內(nèi)質(zhì)網(wǎng)的蛋白質(zhì)和脂肪,然后對它們進行修飾和分選,它所完成的是內(nèi)質(zhì)網(wǎng)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(nèi)體是由內(nèi)吞作用產(chǎn)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(zhì),這種細胞器一般位于細胞質(zhì)的外側(cè)。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(nèi)膜系統(tǒng)的動態(tài)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(zhì)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(nèi)質(zhì)網(wǎng),而分泌蛋白的合成起始于粗面內(nèi)質(zhì)網(wǎng),完成于高爾基體。②分泌活動:③內(nèi)吞活動(endocytosispathway),是分泌的相反過程,細胞將細胞外的物質(zhì)吞進內(nèi)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(dǎo)(embryonicinduction):胚胎發(fā)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(fù)雜的模式由細胞間相互作用產(chǎn)生誘導(dǎo)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(chǎn)生抑素,抑制相鄰細胞發(fā)生同樣的分化；（3）細胞數(shù)量效應(yīng)；（4）細胞外基質(zhì)的影響；（5）激素的作用3.染色體與細胞分化：（1）染色體結(jié)構(gòu)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(zhì)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(jié)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(jié)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(guān)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(guān)，這類基因?qū)毎陨砩鏌o直接影響。管家基因(housekeepinggene)：這類基因的表達產(chǎn)物為細胞生命活動持續(xù)需要和必不少，但與細胞分化的關(guān)系不大，在細胞分化中只起協(xié)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(jié)果。某些基因的選擇性表達合成了執(zhí)行特定功能的蛋白質(zhì)，從而產(chǎn)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?；虻囊环N突變形式，能引起正常細胞癌變。二抑癌基因?qū)嶋H上是正常細胞增殖過程中的負調(diào)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(diào)控作用，則導(dǎo)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(jié)合到原癌基因的啟動子或增強子等位點，使轉(zhuǎn)錄復(fù)合物不能結(jié)合到這些位點，從而不能完成轉(zhuǎn)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(xié)同作用，共同調(diào)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（?。┙z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(jīng)計算機圖象處理，獲得三維影像。3.ultrastructure超微結(jié)構(gòu)答案：細胞從亞顯微水平到分子水平的結(jié)構(gòu)的統(tǒng)稱，亦稱亞顯微結(jié)構(gòu)（submicroscopicstructure）。4.liposome脂質(zhì)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(zhuǎn)分化答案：(1)已分化細胞經(jīng)去分化后再分化成另一種細胞的現(xiàn)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(xiàn)象。6.dockingprotein停泊蛋白答案：內(nèi)質(zhì)網(wǎng)膜上的信號識別顆粒受體。7.thylakoid類囊體答案：葉綠體基質(zhì)中由單位膜封閉形成的扁平囊。8.nuclearporecomplex核孔復(fù)合體答案：核被膜上溝通核質(zhì)和細胞質(zhì)的復(fù)雜隧道結(jié)構(gòu)，由多種核孔蛋白構(gòu)成。隧道的內(nèi)、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(zhì)有控制作用。9.cytoplast,cytosome胞質(zhì)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(zhì)的關(guān)系10．a(chǎn)xonaltransport細胞器或分子沿神經(jīng)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(fā)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(diào)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(huán)境因素相聯(lián)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(tài)的G1進入DNA合成期，相關(guān)的事件包括：DNA是否損傷？細胞外環(huán)境是否適宜？細胞體積是否足夠大？S期檢驗點：DNA復(fù)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(guān)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(zhì)比例增大，分裂速度加快，結(jié)果破壞了正常組織的結(jié)構(gòu)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(huán)或通過淋巴途徑轉(zhuǎn)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(xiàn)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(guān)的蛋白。5.mRNA轉(zhuǎn)錄譜系的改變：基因表達和調(diào)控方向的改變。體外培養(yǎng)的惡性轉(zhuǎn)化細胞的特征：人工誘導(dǎo)培養(yǎng)的惡性轉(zhuǎn)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(xù)分泌3.Targetcells答案：靶細胞4.Triggerprotein答案：觸發(fā)蛋白5.generaltranscriptionfactors答案：通用轉(zhuǎn)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(zhì)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(diào)蛋白（鈣調(diào)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(jié)構(gòu)答案：細胞從亞顯微水平到分子水平的結(jié)構(gòu)的統(tǒng)稱，亦稱亞顯微結(jié)構(gòu)（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(zhì)細胞答案：神經(jīng)系統(tǒng)中的支持細胞，包括脊椎動物中樞神經(jīng)系統(tǒng)中的少突膠質(zhì)細胞和星形膠質(zhì)細胞以及周圍神經(jīng)系統(tǒng)中的雪旺細胞。6.dockingprotein停泊蛋白答案：內(nèi)質(zhì)網(wǎng)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(zhì)膜的薄片狀突起，內(nèi)部有肌動蛋白絲網(wǎng)絡(luò)的支撐，與細胞運動有關(guān)。8.myofibril肌原纖維答案：由粗肌絲和細肌絲規(guī)則排列構(gòu)成的肌纖維亞單位。9.cytoplast,cytosome胞質(zhì)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(zhì)的關(guān)系。10.axonaltransport軸突運輸答案：細胞器或分子沿神經(jīng)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(zhì)，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(zhì)小體，又稱性染色質(zhì)小體(sex-chromatinbody)；1949年為M.Barr所發(fā)現(xiàn)。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(zhì)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(jié)果，請舉例說明分化時特異基因的表達調(diào)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(tài)結(jié)構(gòu)上至少由互相聯(lián)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(xù)分支狀的網(wǎng)結(jié)構(gòu)，接受來自內(nèi)質(zhì)網(wǎng)新合成的物質(zhì)并將其分類后大部分轉(zhuǎn)入高爾基體中間膜囊，小部分蛋白質(zhì)與脂質(zhì)再返回內(nèi)質(zhì)網(wǎng)；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(guān)的多糖的合成的場所；3， 高爾基體反面膜囊參與蛋白質(zhì)的分類與包裝最后由高爾基體輸出。功能：合成糖類；將內(nèi)質(zhì)網(wǎng)合成的多種蛋白質(zhì)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(zhì)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(zhì)膜的分子結(jié)構(gòu)及其基本特性5.核糖體各活性部位及其在蛋白質(zhì)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