生物专业英语第三版蒋悟生课文翻译精华整理

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1、---Mostofthepropertiesweassociatewithlifearepropertiesofthecytoplasm.Muchofthemassofacellconsistsofthissemifluidsubstance,whichisboundedontheoutsidebytheplasmamembrane.Organellesaresuspendedwithinit,supportedbyt..ofthecytoskeleton.Dissolvedinluidarenutrients,ions,solubleproteins,andothermaterialsnee

2、dedforcellfunctioning.生命的大部分特征表现在细胞质的特征上。细胞质大部分由半流体物质组成，并由细胞膜包被。细胞器悬浮在其中，并由丝状的细胞骨架支撑。细胞质中溶解了大量的营养物质、离子、可溶蛋白以及维持细胞生理需求的其它物质。Theeukaryoticcellnucleusisthelargestorganelleandhousesthegeneticmaterial(DNA)onchromosomes.(Inprokaryotesthehereditarymaterialisfoundinthenucleoid.)Thenucleusalsocontainsoneortw

3、oorganelles-thenucleoli-thatplayaroleincelldivision.Apore-perforatedsaccalledthenuclearenvelopeseparatesthenucleusanditscontentsfromthecytoplasm.Smallmoleculescanpassthroughthenuclearenvelope,butlargermoleculessuchasmRNAandribosomesmustenterandexitviathepores.真核细胞的细胞核是最大的细胞器，为染色体上遗传物质（DNA）提供空间（原核生物遗

4、传物质存在于拟核中）。细胞核含有一或二个核仁，在细胞分裂中发挥作用。一个穿孔的囊叫核膜，将细胞核和其中内含物与细胞质分开，小分子物质可以自由通过核膜，但大分子物质如mRNA和核糖体必须通过核孔进出核膜。Alleukaryoticcellscontainmostofthevariouskindsoforganelles,andeachorganelleperformsaspecializedfunctioninthecell.Organellesdescribedinthissectionincluderibosomes,theendoplasmicreticulum,theGolgicompl

5、ex,vacuoles,lysosomes,mitochondria,andtheplastidsofplantcells.所有的真核细胞都含有多种细胞器，每种细胞器在细胞中行使一项专门功能。本节主要介绍核糖体、内质网、高尔基体系、液泡、溶酶体、线粒体和植物细胞中的质体。Thenumberofribosomeswithinacellmayrangefromafewhundredtomanythousands.Thisquantityreflectsthefactthat,ribosomesarethesitesatwhichaminoacidsareassembledintoproteinsf

6、orexportorforuseincellprocesses.Acompleteribosomeiscomposedofonelargerandonesmallersubunit.DuringproteinsynthesisthetwosubunitsmovealongastrandofmRNA,"reading"thegeneticsequencecodedinitandtranslatingthatsequenceintoprotein.SeveralribosomesmaybecomeattachedtoasinglemRNAstrand;suchacombinationiscalle

7、dapolysome.Mostcellularproteinsaremanufacturedonribosomesinthecytoplasm.Exportableproteinsandmembraneproteinsareusuallymadeinassociationwiththeendoplasmicreticulum.细胞中核糖体的数量变化从几百到几千，核糖体数量如此之多反映了核糖体是氨基