生物专业英语课文翻译文档格式.docx

1、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: Information Central（细胞核：信息中心）The eukaryotic cell nucleus is the largest organelle and houses the genetic material （DNA） on chromosomes. （In prokaryotes the hereditary material is found in the nucleoid.） The nucleus also contains one or two organelle

2、s-the nucleoli-that play a role in cell division.A pore-perforated sac called the nuclear envelope separates the nucleus and its contents from the cytoplasm.Small molecules can pass through the nuclear envelope, but larger molecules such as mRNA and ribosomes must enter and exit via the pores.真核细胞的细

3、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。Organelles: Specialized Work Units（细胞器：特殊的功能单位）All eukaryotic cells contain most of the various kinds of organelles, and each organelle performs a specialized function in the cell.Organelles des

4、cribed in this section include ribosomes, the endoplasmic reticulum, the Golgi complex, vacuoles, lysosomes, mitochondria, and the plastids of plant 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 number of ribosomes within a cell may range from a few hundred to many t

5、housands.This quantity reflects the fact that, ribosomes are the sites at which amino acids are assembled into proteins for export or for use in cell processes.A complete ribosome is composed of one larger and one smaller subunit.During protein synthesis the two subunits move along a strand of mRNA,

6、 reading the genetic sequence coded in it and translating that sequence into protein.Several ribosomes may become attached to a single mRNA strand; such a combination is called a polysome.Most cellular proteins are manufactured on ribosomes in the cytoplasm.Exportable proteins and membrane proteins

7、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。核糖体沿着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 membranous sacs, tubules, and vesicles, may be either roug

8、h （RER） or smooth （SER）.Both types play roles in the synthesis and transport of proteins.The RER, which is studded with polysomes, also seems to be the source of the nuclear envelope 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 polyso

9、mes; it is active in the synthesis of fats and steroids and in the oxidation of toxic substances in the cell.Both types of endoplasmic reticulum serve as compartments within the cell where specific products can be isolated and subsequently shunted to particular areas in or outside the cell.光滑内质网上无核糖

10、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。Transport vesicles may carry exportable molecules from the endoplasmic reticulum to another membranous organelle, the Golgi complex.Within the Golgi complex molecules are modified and packaged for export out of the cell or for delivery else where

11、 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 plant cells and serve as water reservoirs and storage sites for sugars and other mole

12、cules.Vacuoles in animal cells carry out phagocytosis （the intake of particulate matter） and pinocytosis （vacuolar drinking）.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 enzymes （packaged in

13、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 reactions in all cells.In addition, plant cells co

14、ntain plastids that utilize light energy to manufacture 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.Mitochondria are self-replicating, and probably they are the evolutionary desce

15、ndants 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 pigments and serve as storage sites for starch, proteins, and oils; and chromoplasts, which c

16、ontain pigments.The most important chromoplasts are chloroplasts-organelles that contain the chlorophyll used in photosynthesis.The internal structure of chloroplasts includes stacks of membranes called grana, 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。

17、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 Cytoskeleton（细胞骨架）All eukaryotic cells have a cytoskeleton, which is a convoluted latticework of filaments and tubules that appears to fill all available space in the cell and provides support for various other organelles.A large por

18、tion of the cytoskeleton consists of threadlike microfilaments composed mainly of the contractile 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 compone

19、nt of the cytoskeleton consists of microtubules, which are composed of the globular protein tubulin and together act as scaffolding that provides a stable cell shape.Cytoskeletal intermediate filaments appear to impart tensile strength to the cell cytoplasm.Mechanoenzymes such as myosin, dynein, and

20、 kinesin interact with the cytoskeletal filaments and tubules to generate forces that cause movements.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

21、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 to cells, its microtubules and filaments and their associated proteins enable cells to move by creeping or gliding.Such movements require a solid substrate to which the cell can adhere and can be

22、guided by the geometry of the surface.Some cells also exhibit chemotaxis, the ability to move toward or away from the source of a diffusing 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。Certain eukaryotic cells can swim freely in liquid environmen

23、ts, propelled by whiplike cilia or flagella. Both cilia and flagella have the same internal structure: nine doublets （pairs of microtubules） are arranged in a ring and extend the length of the cilium or flagellum, and two more microtubules run down the center of the ring. Every cilium or flagellum g

24、rows only from the cell surface where a basal body is located. Movement is based on the activities of tiny dynein side arms that extend from one of the microtubules of each doublet.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。Nutrien

25、ts, proteins, and other materials within most plant cells are moved about via cytoplasmic streaming. The process occurs as myosin proteins attached to organelles push against microfilaments arrayed throughout the cell. Microfilaments and microtubules are responsible for almost all major cytoplasmic

26、movements. During cell division, microtubules of the spindle assembled from tubutin subunits near organelles 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。第二课Photosynthesis occurs only in th

27、e chlorophyll-containing cells of green plants, algae, and certain protists and bacteria.Overall, it is a process that converts light energy into chemical energy that is stored in the molecular bonds.From the point of view of chemistry and energetics, it is the opposite of cellular respiration.Where

28、as cellular respiration is highly exergonic and releases energy, photosynthesis requires energy and is highly endergonic.光合作用只发生在含有叶绿素的绿色植物细胞，海藻，某些原生动物和细菌之中。总体来说，这是一个将光能转化成化学能，并将能量贮存在分子键中，从化学和动能学角度来看，它是细胞呼吸作用的对立面。细胞呼吸作用是高度放能的，光合作用是需要能量并高吸能的过程。Photosynthesis starts with CO2 and H2O as raw materials a

29、nd proceeds through two sets of partial reactions.In the first set, called the light-dependent reactions, water molecules are split （oxidized）, 02 is released, and ATP and NADPH are formed.These reactions must take place in the presence of light energy.In the second set, called light-independent rea

30、ctions, CO2 is reduced （via the addition of H atoms） to carbohydrate.These chemical events rely on the electron carrier NADPH and ATP generated by the first set of reactions.光合作用以二氧化碳和水为原材料并经历两步化学反应。第一步，称光反应，水分子分解，氧分子释放，ATP和NADPH形成。此反应需要光能的存在。第二步，称暗反应，二氧化碳被还原成碳水化合物，这步反应依赖电子载体NADPH以及第一步反应产生的ATP。Both sets of reactions take place in chloroplasts.Most of the enzymes and pigments for the lightdependent reactions are embedded in the thylakoid membrane of chloroplasts.The dark reactions take place in the stroma.两步反应都发生在叶绿体中。光反应需要的大部分酶和色素包埋在叶绿体的类囊体膜上。暗反应发生在基质中。How Light Energy Rea