生物专业英语第三版蒋悟生编__课文翻译

In side the Livi ng Cell: Structure and

Fun cti on of Internal Cell Parts

Cytoplasm: The Dyn amic, Mobile Factory 细胞质：动力工厂Most of the properties we associatewith life are properties of the cytoplasm. Much of the mass of a cell consists of this semifluid substanee, which is bounded on the outside by the plasma membrane. Organelles are suspended within it, supported by the filamentous network of the cytoskeleton. Dissolved in the cytoplasmic fluid are nutrients, ions, soluble prote ins, and other materials n eeded for cell fun cti oning. 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（原生质膜）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。

The Nucleus: In formation Central （细胞核：信息中心）The eukaryotic cell nucleus is the largest orga nelle and houses the gen etic material （DNA） on chromosomes（l n prokaryotes the hereditary material is found in the nucleoid ?）The nu cleus also contains one or two orga nelles-the nucleolit hat play a role in cell division. A pore-perforated sac called the nuclear envelope separates the nu cleus and its contents from the cytoplasm. Small molecules can pass through the nuclear envelope, but larger molecules such as mRNA and ribosomes must en ter and exit via the pores.

真核细胞的细胞核是最大的细胞器，细胞核对染色体组有保护作用（原核细胞的遗传物质存在于拟核中）。细胞核含有一或二个核仁，核仁促进细胞分裂。核膜贯穿许多小孔，小分子可以自由通过核膜，而象mRNA和核糖体等大分子必须通过核孔运输。

Orga nelles: Specialized Work Un its （细胞器：特殊的功能单位）All eukaryotic cells contain most of the various kinds of orga nelles, and each orga nelle performs a specialized fun cti on in the cell. Orga nelles described in this secti on in elude ribosomes, the

endoplasmic reticulum, the Golgi complex, vacuoles, lysosomes, mitoch on dria, and the plastids of pla nt cells.

所有的真核细胞都含有多种细胞器，每个细胞器都有其特定功

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。

The nu mber of ribosomes withi n a cell may range from a few hundred to many thousands. This quantity reflects the fact that, ribosomes are the sites at which amino acids are assembledi nto proteins for export or for use in cell processes. A complete ribosome is composed of one larger and one smaller subunit. During protein syn thesis the two sub un its move along a stra nd of mRNA, "readi ng" the gen etic seque nee coded in it and tran slat ing that sequenee into protein. Several ribosomes may become attached to a sin gle mRNA stra nd; such a comb in ati on is called a polysome.

Most cellular proteins are manufactured on ribosomes in the cytoplasm. Exportable protei ns and membra ne proteins are usually made in association with the endoplasmic reticulum.

核糖体的数量变化从几百到几千，核糖体是氨基酸组装成蛋白质

的重要场所。完整的核糖体由大亚基和小亚基组成。核糖体沿看mRNA移动并阅读遗传密码，翻译成蛋白质。一条mRNA上可能有多个核糖体，称多聚核糖体。大多数细胞蛋白是由细胞质中核糖体生产。输出蛋白和膜蛋白通常与内质网有关。

The endoplasmic reticulum,a lacy array of membra nous sacs, tubules, and vesicles, may be either rough (RER) or smooth (SER). Both types play roles in the syn thesis and tran sport of prote ins. The RER, which is studded with polysomes, also seems to be the source of the nu clear en velope after a cell divides.

内质网，带有花边的生物囊，有管状，泡状之分，以及光滑和粗

糙面区别。两种都与蛋白质的合成和运输有关。粗糙内质网上分布许多核糖体，也可能提供细胞分裂后所需的细胞膜。

SER lacks polysomes; it is active in the syn thesis of fats and steroids and in the oxidati on of toxic substa nces in the cell. Both

types of en doplasmic reticulum serve as compartme nts withi n the cell where specific products can be isolated and subsequently shu nted to particular areas in or outside the cell.

光滑内质网上无核糖体，主要作用是脂肪和类固醇的合成以及细胞内有毒物质的氧化。两种内质网合成的产物在其中进行分流或运输到细胞外。

Tran sport vesicles may carry exportable molecules from the en doplasmic reticulum to ano ther membra nous orga nelle, the Golgi complex. Within the Golgi complex molecules are modified and packaged for export out of the cell or for delivery else where in the cytoplasm.

运输小泡能够将可运输分子从内质网运输到高尔基复合体上。在高尔基复合体中修饰，包装后输出细胞或传递到细胞质中的其他场所。Vacuoles in cells appear to be hollow sacs but are actually filled with fluid and soluble molecules. The most prominent vacuoles appear in pla nt cells and serve as water reservoirs and storage sites for sugars and other molecules. Vacuoles in animal cells carry out phagocytosis (the in take of particulate matter) and

pinocytosis(vacuolar drinkin g).

细胞中的液泡好象是中空的，但实际上充满了液体和可溶分子。最典型的液泡存在于植物细胞中，储备水，糖以及其它分子。动物中的液泡起吞噬和胞饮作用。

A subset of vacuoles are the organelles known as lysosomes, which contain digestive en zymes (packaged in lysosomes in the Golgi complex) that can break down most biological macromolecules. They act to digest food particles and to degrade damaged cell parts.

溶酶体是液泡亚单位，含有消化酶，降解大部分生物大分子。消化食物微粒和降解损伤的细胞残片。

Mitochondria are the sites of energy-yielding chemical reacti ons in all cells. In additi on, pla nt cells contain plastids that utilize light en ergy to manu facture carbohydrates in the process of photosynthesis. It is on the large surface area provided by the inner

cristae of mitochondria that ATP-generating enzymes are located. Mitoch on dria are self-replicati ng, and probably they are the evolutionary descendants of what were once free-living prokaryotes. 线粒体是细胞中化学产能的场所。另外，植物细胞中的质体在光合作用中利用光能产生碳水化合物，线粒体内嵴上提供了

很大的表面积并分布着产ATP酶。线粒体自我复制，并且可能是自由生活的原核生物在进化中形成的后代。

There are two types of plastids: leucoplasts, which lack pigme nts and serve as storage sites for starch, prote ins, and oils; and chromoplasts, which contain pigments. The most important chromoplasts are chloroplasts organelles that contain the chlorophyll used in photosynthesis. The internal structure of chloroplasts in cludes stacks of membra nes calledra na, which are embedded in a matrix called the stroma.

质体有两种类型：白色体，缺乏色素，是淀粉，蛋白质和油的储备场所；色质体，含有色素。叶绿体是最重要的色质体，含有与光合作用有关的叶绿素。叶绿体的内部结构是由多层膜形成的叶绿体基粒，其中包埋在基质中的基粒称子座。

The Cytoskeleto n （细胞骨架）

All eukaryotic cells have a cytoskelet on, which is a con voluted latticework of filaments and tubules that appears to fill all available space in the cell and provides support for various other organelles. A large portion of the cytoskeleton consists of threadlike microfilaments composed mai nly of the con tractile protein actin. They are involved in many types of intracellular movements in plant and animal cells. A second protein, myosin, is involve in the contraction of muscle cells. Another main structural comp onent of the cytoskelet on con sists of nicrotubules, which are composed of the globular protein tubulin and together act as scaffolding that provides a stable cell shape. Cytoskeletal in termediate filame nts appear to impart ten sile stre ngth to the cell cytoplasm. Mechanoenzymes such as myosin, dynein, and kin esi n in teract with the cytoskeletal filame nts and tubules to gen erate

forces that cause moveme nts.

所有的细胞都有细胞骨架，网络结构的纤丝充满了它所能触及的全部空间并且对细胞器提供支持作用。细胞骨架大部分由微

丝组成，微丝主要由可收缩的肌动蛋白组成。动植物细胞的许多种类型细胞内运动与肌动蛋白有关。第二类蛋白是肌球蛋白，它与肌肉细胞的收缩有关。细胞骨架的另一个主要结构成分是微管，由球状的微管蛋白组成，象脚手架一般维持细胞的稳定形态。细胞骨架的中间丝提供了细胞质伸缩动力。机械酶，

例如，肌球蛋白，动力蛋白，驱动蛋白与微丝，微管相互作用产生动力而引起细胞运动。

Cellular Movements （细胞运动

Although the cytoskeleton provides some stability 稳固to cells, its microtubules

英［?maikr ?u?tju:bju:l ］ and filaments 丝状物and their associated prote ins en able cells to move by creep in爬行or gliding 滑动. Such movements require a solid固体的substrate to which the cell can adhere附着and can be guided by the geometry d?i??mitri ］

几何形状of the surface. Some cells also exhibit ［i g ?zibit 展览chemotaxis,kem ??? ksis 趋药性the ability to move toward or away from the source of a diffus ing 扩散chemical.

尽管细胞骨架提供了细胞的某些稳定性，微丝，微管及相关蛋白能使细胞爬行或滑动。这种运动需要固体基质依托并通过表面几何形状的改变而运动。某些细胞具备趋药性，即趋向或逃离扩散开的化学源。

Certai n eukaryotic cells can swim freely in liquid en vir onmen ts, propelled by whiplike cilia ［⑥li ?］纤毛or flagella 英［fl ??d ?el ?

鞭毛.Both cilia and flagella have the same in ternal structure: nine doublets (pairs of microtubules) arearra nged in a ring and exte nd the len gth of the cilium or flagellum, and two more microtubules run dow n the cen ter of the ring. Every cilium or flagellum grows only

from the cell surface where a basal body基体is located. Movement is based on the activities of tiny dynein动力蛋白side arms that exte nd from one of the microtubules of each double成对的东西.

某些真核细胞能在液体液体中自由运动，由纤毛或鞭毛推动。纤毛和鞭毛具有同样的内部结构：九个双微管环形排列，纵向延伸，环中心是两个或以上微管组成。纤毛或鞭毛从细胞表面的基体出生长，双微管的动力蛋白臂从一侧延伸到另一侧而引起运动。

Nutrie nts, prote ins, and other materials within most pla nt cells are moved about via cytoplasmic stream ing. The process occurs as myosin ?mai ?usin 肌凝蛋白proteins attached to organelles纟田胞器，小器官push against microfilaments arrayeq??*ei ] 展示throughout the cell. Microfilame nts and microtubules are resp on sible for almost all majorcytoplasmic moveme nts. During cell divisi on, microtubules of the spin dle assembled 集合, 收集from tubuti n sub un its n ear orga nelles called centrioles move the chromosomes.

大部分植物细胞的营养，蛋白质和其它物质由细胞质流运输。这个过程是由于依附在细胞器上的肌球蛋白反推排列在细胞周围的微丝形成的。绝大部分细胞质运动由微丝和微管完成。在细胞分裂期间，中心粒周围的由微管蛋白亚基装配形成的纺锤体微管移向染色体。

Glossary

cytoplasm （纟田）胞质

The living contents of a cell bounded externally by the plasmalemma, in cludi ng an aqueous ground substa nee (hyaloplasm, cell sap, or cell matrix) containing organelles and various in clusi ons but excludi ng the nu cleus and visible vacuoles. cytoskeleton 细胞骨架

Of eukaryotic cells, an in ternal "skeleto n". Its microtubules and

other comp onents structurally support the cell, orga nize and move its inteftial components. The cytoskeleton also helps free-living cells move through their en vir onment.

nucleus 细胞核，核(复数nuclei)

The orga nelle of the eukaryote cell that contains the chromosomes and hence ultimately con trols cellular activity and in herita nee through the activity of the gen etic material, DNA chromosome 染色体

A DNA-histone thread residing in the nucleus of a cell. Each chromosome possesses two telomeres and a cen tromere, and some contain a nu cleolus orga ni zer. RNA prote ins are in variably associated with the chromosome.

nucleoid 拟核，类核，核质体

The DNA-c ontaining area of a prokaryote cell, an alogous to the eukaryote nu cleus but not membra ne boun ded.

nucleoli 核仁(单数nucleolus

Nuclear structures composed of completed or partially completed ribosomes and the specific parts of chromosomes that contain the infon-n ati on for their con structi on.

nuclear envelope 核膜，核被膜

A double membra ne (two lipid bilayers and associated protei ns) that is the outermost porti on of a cell nu cleus.

ribosome 核糖体

Small structures composed of two prote in and ribonu cleic acid sub un its in volved in the assembly of prote ins from amino acids. polysome 多核糖体

Of protein syn thesis, several ribosomes all tran slati ng the same messe nger RNA molecule,o ne after the other.

endoplasmic reticulum 内质网

Folded membra nes and tubes throughout the eukaryotic cell that provide a large surface upon which chemical activities take place. Golgi complex 高尔基复合体

A stack of flatte ned, smooth, membra nous sacs; the site of syn

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