UNIT1AlthoughtheDNAinthenucleusofeachcellcontainsallofthegeneticinformationforallhumantraits,onlyasmallnumberofgenesareactuallyactiveinaparticularcell.Theseactivegenesarethecodesfortheproteinsnecessaryforthespecificcelltype.盡管每一個細胞核中的DNA都包含有人類特性的所有遺傳信息，但實際上只有小數基因在特定細胞中有活性，這些活性基因是特有的細胞類型所必須的蛋白密碼。Infacilitateddiffusion,moleculesmovethroughamembranefromanareaofgreaterconcentrationtoanareaoflesserconcentration,buttheyneedsomehelptodothis.在易化擴散中，大分子經一層膜從高濃度區域向低濃度區域移動，但分子要完成這一工作需要某些幫助。Thecellmembraneisselectivelypermeable,thatis,certainsubstancesarepermittedtopassthroughandothersarenot.細胞膜的滲透性是有選擇性的，即某些物質允許通過，而其它物質則不行。Filtrationmeansthatwateranddissolvedmaterialsareforcedthroughamembranefromanareaofhigherpressuretoanareaoflowerpressure.過濾是指水和已溶解物質經一層膜從高壓區壓送到低壓區。5.ActivetransportrequirestheenergyofATPtomovemoleculesfromanareaoflesserconcentrationtoanareaofgreaterconcentration.主動轉運需要ATP這種能使分子從低濃度區向高濃度區移動。1.體內平衡取決于所有不同類型的細胞正常的發揮其功能。(dependupon)Homeostasisdependsuponthenormalfunctionsofallofthedifferentkindsofcells.2.就人口和地域而言，這兩個國家差異很大。(withrespectto)Withrespecttopopulationandgeographicalarea,thesetwocountriesvarygreatly.3.染色體由脫氧核糖核酸和蛋白構成，而脫氧核糖核酸又是細胞特征和活性的遺傳密碼。(geneticcode)ChromosomesaremadeofDNAandprotein,andtheDNAisthegeneticcodeforthecharacteristicsandactivitiesofthecell.4.氧氣從空氣中擴散到血液以便在全身循環，而二氧化碳從血液散播到空氣中以便排出體外。(diffuse)Oxygendiffusesfromtheairtothebloodtobecirculatedthroughoutthebody,butcarbondioxidediffusesfromthebloodtotheairtobeexhaledfromthebody.5.科學不斷地提供新的發現，從而進一步支持了他的假設。(backup)Sciencecontinuedtothrowupdiscoverieswhichfurtherbackeduphishypothesis.UNIT21.Ateitherendoftheagespectrum,however,temperatureregulationmaynotbeaspreciseasitisinolderchildrenoryoungeradults.然而，在年齡段兩端的人群，其體溫調節精確程度都不如青少年或青年人。2.Thepathwaysofheatlossfromthebodyaretheskin,respiratorytract,andtoalesserextent,theurinaryanddigestivetracts.人體散熱途徑是經皮膚、呼吸道，少量經尿道和消化道散熱。3.Changesinbodytemperaturealsohaveaneffectonmetabolicrateandheatproduction.Thisbecomesclinicallyimportantwhenapersonhasafever,anabnormallyhighbodytemperature.人體體溫的變化也會影響代謝率和產熱。當一個人發熱、體溫異常升高時，從臨床上講，體溫變化就顯得重要了。4.Anabolismmeanssynthesisor“formation”reactions,thebondingtogetherofsmallermoleculestoformlargerones.合成代謝是指綜合或“形成”性反應，即把小的分子結合在一起形成更大的分子。5.Catabolismmeansdecomposition,thebreakingofbondsoflargermoleculestoformsmallermolecules.Cellrespirationisaseriesofcatabolicreactionsthatbreakdownfoodmoleculestocarbondioxideandwater.分解代謝是指分解，即將較大的分子鏈分解形成小分子。細胞呼吸過程就是一連串的分解代謝反應---將食物分子分解成二氧化碳和水。1.新陳代謝是指發生在生物體內的化學過程，可分為合成代謝和分解代謝兩大類。(metabolism)Metabolismreferstothechemicalreactionsthattakeplaceinthelivingorganisms.Itmaybedividedintotwomajorcategories:anabolismandcatabolism.2.正常人的體溫為37度。隨個體、年齡、活動量和每日早晚略有差異，但波動幅度不超過l℃。(fluctuation)Thenormalbodytemperatureis37oC,andvariesbyperson,age,activity,andtimeofday,butthefluctuationsareusuallynomorethan1.0oC.3.在正常情況下，人體通過體溫調節系統使體溫保持相對穩定。(constant)Undernormalconditions,humanbodyisabletomaintainarelativelyconstantbodytemperaturethroughthesystemoftemperatureregulation.4.與生活在熱帶地區的人相比，在寒冷氣候下生活的人，新陳代謝率要高10-20%。(metabolicrate)Peoplewholiveincoldclimatesmayhavemetabolicrates10%to20%higherthanthosewholiveintropicalregions.5.人體體溫的調節主要是通過汗腺的分泌及皮膚血管的收縮與舒張。(excretion)HumanbodytemperatureismainlyregulatedthroughtheexcretionofsweatglandandvasodilationandconstrictionofbloodvesselsintheskinUNIT31.VentricularcontractionforcesbloodagainsttheflapsoftherightandleftAVvalvesandclosesthem;theforceofbloodalsoopenstheaorticandpulmonarysemilunarvalves.心室收縮使血液施壓于左右房室瓣并使其關閉；血液的壓力也使主動脈半月瓣和肺動脈半月瓣打開。2.Palpationsareusuallynotserious,andmaybetheresultoftoomuchcaffeine,nicotine,oralcohol.Muchmoreseriousisventricularfibrillation,averyrapidanduncoordinatedventricularbeatthatistotallyineffectiveforpumpingblood.心悸通常不很嚴重，可能因攝入的咖啡因，尼古丁