細(xì)胞生物學(xué)歷年真題試卷

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(xì)胞器6.Targetcells答案：靶細(xì)胞7.F0-F1couplingfactor答案：F0-F1偶聯(lián)因子8.Primarylysosome答案：初級(jí)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(xì)胞，它可生成神經(jīng)元、星形膠質(zhì)細(xì)胞、少突膠質(zhì)細(xì)胞。亦可轉(zhuǎn)分化成血細(xì)胞和骨骼肌細(xì)胞。2.XinactivationX答案：雌性成體細(xì)胞中兩條X染色體中的一條處于正常失活狀態(tài)。3.cellline細(xì)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(xì)胞群。一般為腫瘤細(xì)胞或轉(zhuǎn)化細(xì)胞形成。4.polymorphicnucleus多形核答案：哺乳動(dòng)物顆粒白細(xì)胞中形狀不規(guī)則的核。5.voltage-gatedionchannel電壓門控通道答案：興奮細(xì)胞質(zhì)膜上的一種離子通道，對(duì)跨膜電位差的變化極為敏感，因膜電位達(dá)到一定閾值而開放。6.contractileprotein收縮蛋白答案：細(xì)胞中參與收縮過程的蛋白質(zhì)，如肌動(dòng)蛋白和肌球蛋白。7.cellcoat答案：又稱糖萼（glycocalyx），動(dòng)物細(xì)胞質(zhì)膜外的一層黏多糖物質(zhì)，以共價(jià)鍵和膜蛋白或膜脂結(jié)合形成糖蛋白或糖脂，它對(duì)膜蛋白有保護(hù)作用，并在分子識(shí)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(xì)胞內(nèi)信號(hào)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(xì)胞黏附答案：動(dòng)物細(xì)胞通過細(xì)胞表面的黏附分子介導(dǎo)細(xì)胞之間或細(xì)胞與細(xì)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(xì)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(xì)胞內(nèi)膜結(jié)合細(xì)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(xì)胞核位于細(xì)胞的中央,它是細(xì)胞中最重要的細(xì)胞器,有兩層膜結(jié)構(gòu)。細(xì)胞核的外膜與內(nèi)質(zhì)網(wǎng)的膜是聯(lián)系在一起的,細(xì)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(xì)胞核,所以內(nèi)質(zhì)網(wǎng)位于細(xì)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(duì)它們進(jìn)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(xì)胞器,它能向溶酶體傳遞從細(xì)胞外攝取的物質(zhì),這種細(xì)胞器一般位于細(xì)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(xì)胞的不同部位。如果是植物細(xì)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(dòng)態(tài)特性主要是由細(xì)胞中三種不同的生化活動(dòng)引起的:①蛋白質(zhì)和脂的合成活動(dòng):在動(dòng)物細(xì)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(dòng):③內(nèi)吞活動(dòng)(endocytosispathway),是分泌的相反過程,細(xì)胞將細(xì)胞外的物質(zhì)吞進(jìn)內(nèi)體和溶酶體。2.Whatiscelldifferentiation？Pleaseintroducethemechanism.答：1.細(xì)胞分裂的不對(duì)稱性：在細(xì)胞分裂時(shí)一些重要的分子被不均等地分配到兩個(gè)子細(xì)胞中2.細(xì)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(xì)胞影響相鄰細(xì)胞向一定方向分化的作用.進(jìn)一步更復(fù)雜的模式由細(xì)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(xì)胞中建立起有序的差異；（2）分化抑制:分化成熟的細(xì)胞可以產(chǎn)生抑素,抑制相鄰細(xì)胞發(fā)生同樣的分化；（3）細(xì)胞數(shù)量效應(yīng)；（4）細(xì)胞外基質(zhì)的影響；（5）激素的作用3.染色體與細(xì)胞分化：（1）染色體結(jié)構(gòu)的變化；（2）基因刪除:原生動(dòng)物,昆蟲,甲殼動(dòng)物；（3）基因擴(kuò)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(xì)胞分化無論是母體mRNA的作用還是細(xì)胞間的相互作用,其結(jié)果是啟動(dòng)特定基因的表達(dá).母體基因→間隙基因→成對(duì)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(xì)胞中含有決定生長分裂和分化的全部基因信息，按其與細(xì)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(xì)胞特異性蛋白，與各種分化細(xì)胞的特定性狀直接相關(guān)，這類基因?qū)?xì)胞自身生存無直接影響。管家基因(housekeepinggene)：這類基因的表達(dá)產(chǎn)物為細(xì)胞生命活動(dòng)持續(xù)需要和必不少，但與細(xì)胞分化的關(guān)系不大，在細(xì)胞分化中只起協(xié)助作用。從分子層次看，細(xì)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(dá)的結(jié)果。某些基因的選擇性表達(dá)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(xì)胞類型。3.Pleasenarratetherelationshipofoncogeneandtumer-suppressorgene.癌基因是控制細(xì)胞生長和分裂的正常基因的一種突變形式，能引起正常細(xì)胞癌變。二抑癌基因?qū)嶋H上是正常細(xì)胞增殖過程中的負(fù)調(diào)控因子，它編碼的蛋白往往在細(xì)胞周期的檢驗(yàn)點(diǎn)上起阻止周期進(jìn)程的作用。如果抑癌基因突變，喪失其對(duì)細(xì)胞增殖的負(fù)調(diào)控作用，則導(dǎo)致細(xì)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(dòng)子或增強(qiáng)子等位點(diǎn)，使轉(zhuǎn)錄復(fù)合物不能結(jié)合到這些位點(diǎn)，從而不能完成轉(zhuǎn)錄和翻譯，失去了對(duì)細(xì)胞周期的促進(jìn)作用。通過癌基因和抑癌基因的協(xié)同作用，共同調(diào)控細(xì)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(xì)胞3.Determinants答案：決定子4.EScells答案：胚胎干細(xì)胞5.Channelprotein答案：通道蛋白6.actinfilaments答案：肌動(dòng)蛋白絲7.Dedifferentiation答案：脫(去)分化8.Stemcells答案：干細(xì)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(xì)激光束通過物鏡掃描標(biāo)本成像,將不同光切面的影像經(jīng)計(jì)算機(jī)圖象處理，獲得三維影像。3.ultrastructure超微結(jié)構(gòu)答案：細(xì)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(xì)胞經(jīng)去分化后再分化成另一種細(xì)胞的現(xiàn)象，如色素細(xì)胞分化成晶狀體。(2)一種組織的干細(xì)胞能夠分化成他種組織細(xì)胞的現(xiàn)象。6.dockingprotein停泊蛋白答案：內(nèi)質(zhì)網(wǎng)膜上的信號(hào)識(shí)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(xì)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(duì)進(jìn)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(xué)方法，將細(xì)胞核去除后所得到的細(xì)胞部分，可以用來研究細(xì)胞核與細(xì)胞質(zhì)的關(guān)系10．a(chǎn)xonaltransport細(xì)胞器或分子沿神經(jīng)細(xì)胞軸突定向的運(yùn)輸，可以是順向的（從細(xì)胞體向外）或逆向的（向著細(xì)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(dòng)，胚胎發(fā)生了雄性和雌性的性別差異。在哺乳動(dòng)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(qiáng)。分子鏈間的2.Pleaseintroducethemaincheckpointsduringthecellcycle.答：細(xì)胞周期檢驗(yàn)點(diǎn)是細(xì)胞周期調(diào)控的一種機(jī)制,主要是確保周期每一時(shí)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(gè)事件完成之后，才啟動(dòng)下一個(gè)事件。主要檢驗(yàn)點(diǎn)包括：G1/S檢驗(yàn)點(diǎn)：在酵母中稱start點(diǎn)，在哺乳動(dòng)物中稱R點(diǎn)(restrictionpoint)，控制細(xì)胞由靜止?fàn)顟B(tài)的G1進(jìn)入DNA合成期，相關(guān)的事件包括：DNA是否損傷？細(xì)胞外環(huán)境是否適宜？細(xì)胞體積是否足夠大？S期檢驗(yàn)點(diǎn)：DNA復(fù)制是否完成？G2/M檢驗(yàn)點(diǎn)：是決定細(xì)胞一分為二的控制點(diǎn)，相關(guān)的事件包括：DNA是否損傷？細(xì)胞體積是否足夠大？紡錘體組裝檢驗(yàn)點(diǎn)：任何一個(gè)著絲點(diǎn)沒有正確連接到紡錘體上，引起細(xì)胞周期中斷。3.Whatisthebasiccharacteristicsofcancercells?1.細(xì)胞生長與分裂失去控制：癌細(xì)胞的生長與分裂失去控制，成為不死的永生細(xì)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(kuò)散性：癌細(xì)胞粘著性下降，具有侵潤性和擴(kuò)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(xì)胞間相互作用改變：正常細(xì)胞通過細(xì)胞表面特異性蛋白的相互作用識(shí)別，進(jìn)而形成特定的組織與器官。癌細(xì)胞沖破了細(xì)胞識(shí)別作用的束縛，異常表達(dá)某些膜受體蛋白，以便與別處細(xì)胞粘著生長。4.蛋白表達(dá)譜系或蛋白活性改變：出現(xiàn)一些錯(cuò)位表達(dá)的蛋白，具有較高的端粒酶活性，異常表達(dá)與惡性增殖、擴(kuò)散等過程相關(guān)的蛋白。5.mRNA轉(zhuǎn)錄譜系的改變：基因表達(dá)和調(diào)控方向的改變。體外培養(yǎng)的惡性轉(zhuǎn)化細(xì)胞的特征：人工誘導(dǎo)培養(yǎng)的惡性轉(zhuǎn)化細(xì)胞同樣具有無限增殖的能力，貼壁性下降，失去運(yùn)動(dòng)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(xì)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(xì)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(xì)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(dòng)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(xì)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（?。┙z答案：橫紋肌中的肌球蛋白II絲，直徑約12－14nm。2.osteoclast破骨細(xì)胞答案：在生長中的骨的骨髓中形成的一種巨大的多核細(xì)胞，具有破骨功能。osteocyte骨細(xì)胞3.ultrastructure超微結(jié)構(gòu)答案：細(xì)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(xì)胞中廣泛表達(dá)的一種7次穿膜的G蛋白，與趨化因子受體相連，當(dāng)HIV病毒感染T細(xì)胞時(shí)起輔因子的作用。5.glialcells膠質(zhì)細(xì)胞答案：神經(jīng)系統(tǒng)中的支持細(xì)胞，包括脊椎動(dòng)物中樞神經(jīng)系統(tǒng)中的少突膠質(zhì)細(xì)胞和星形膠質(zhì)細(xì)胞以及周圍神經(jīng)系統(tǒng)中的雪旺細(xì)胞。6.dockingprotein停泊蛋白答案：內(nèi)質(zhì)網(wǎng)膜上的信號(hào)識(shí)別顆粒受體。7.lamellipodium片足答案：細(xì)胞表面的外被質(zhì)膜的薄片狀突起，內(nèi)部有肌動(dòng)蛋白絲網(wǎng)絡(luò)的支撐，與細(xì)胞運(yùn)動(dòng)有關(guān)。8.myofibril肌原纖維答案：由粗肌絲和細(xì)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(xué)方法，將細(xì)胞核去除后所得到的細(xì)胞部分，可以用來研究細(xì)胞核與細(xì)胞質(zhì)的關(guān)系。10.axonaltransport軸突運(yùn)輸答案：細(xì)胞器或分子沿神經(jīng)細(xì)胞軸突定向的運(yùn)輸，可以是順向的（從細(xì)胞體向外）或逆向的（向著細(xì)胞體）。11.contractileprotein收縮蛋白答案：細(xì)胞中參與收縮過程的蛋白質(zhì)，如肌動(dòng)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(duì)活體細(xì)胞或組織的染色。13.Barrbody巴（爾）氏小體答案：雌性哺乳動(dòng)物體細(xì)胞在有絲分裂間期的細(xì)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?yàn)槊恳粋€(gè)克隆都來自于一個(gè)B細(xì)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(xì)胞分化是被選定的不同特異基因表達(dá)的結(jié)果，請(qǐng)舉例說明分化時(shí)特異基因的表達(dá)調(diào)控方式2.簡述衰老細(xì)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(qiáng)。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(gè)部分組成，請(qǐng)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(chǎng)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(jìn)行加工分類包裝并運(yùn)送到特定部位或分泌到細(xì)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(qǐng)?jiān)斒黾?xì)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