生物專業(yè)英語第三版蔣悟生編課文翻譯

1、Inside the Living Cell: Structure andFunction of Internal Cell PartsCytoplasm: The Dynamic, Mobile Factory細胞質：動力工廠Most of the properties we associate with life are properties of the cytoplasm. Much of the mass of a cell consists of this semifluid substance, which is bounded on the outside by the pla

2、sma membrane. Organelles are suspended within it, supported by the filamentous network of the cytoskeleton. Dissolved in the cytoplasmic fluid are nutrients, ions, soluble proteins, and other materials needed for cell functioning.生命的大部分特征表現(xiàn)在細胞質的特征上。細胞質大部分由半流體物質組成，并由細胞膜（原生質膜）包被。細胞器懸浮在其中，并由絲狀的細胞骨架支撐。細

3、胞質中溶解了大量的營養(yǎng)物質，離子，可溶蛋白以及維持細胞生理需求的其它物質。The Nucleus: Information Central（細胞核：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 organelles

4、-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.真核細胞的

5、細胞核是最大的細胞器，細胞核對染色體組有保護作用（原核細胞的遺傳物質存在于擬核中）。細胞核含有一或二個核仁，核仁促進細胞分裂。核膜貫穿許多小孔，小分子可以自由通過核膜，而象mRNA和核糖體等大分子必須通過核孔運輸。Organelles: Specialized Work Units（細胞器：特殊的功能單位）All eukaryotic cells contain most of the various kinds of organelles, and each organelle performs a specialized function in the cell. Organelles d

6、escribed in this section include ribosomes, the endoplasmic reticulum, the Golgi complex, vacuoles, lysosomes, mitochondria, and the plastids of plant cells.所有的真核細胞都含有多種細胞器，每個細胞器都有其特定功能。本節(jié)主要介紹核糖體，內(nèi)質網(wǎng)，高爾基體系，液泡，溶酶體，線粒體和植物細胞中的質體。The number of ribosomes within a cell may range from a few hundred to many

7、 thousands. 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

8、mRNA, "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 an

9、d membrane proteins are usually made in association with the endoplasmic reticulum.核糖體的數(shù)量變化從幾百到幾千，核糖體是氨基酸組裝成蛋白質的重要場所。完整的核糖體由大亞基和小亞基組成。核糖體沿著mRNA移動并閱讀遺傳密碼，翻譯成蛋白質。一條mRNA上可能有多個核糖體，稱多聚核糖體。大多數(shù)細胞蛋白是由細胞質中核糖體生產(chǎn)。輸出蛋白和膜蛋白通常與內(nèi)質網(wǎng)有關。The endoplasmic reticulum, a lacy array of membranous sacs, tubules, and vesicles

10、, may be either rough (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.內(nèi)質網(wǎng)，帶有花邊的生物囊，有管狀，泡狀之分，以及光滑和粗糙面區(qū)別。兩種都與蛋白質的合成和運輸有關。粗糙內(nèi)質網(wǎng)上分布許多核糖體，也可能提供細胞分裂后所

11、需的細胞膜。SER lacks polysomes; 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 out

12、side the cell.光滑內(nèi)質網(wǎng)上無核糖體，主要作用是脂肪和類固醇的合成以及細胞內(nèi)有毒物質的氧化。兩種內(nèi)質網(wǎng)合成的產(chǎn)物在其中進行分流或運輸?shù)郊毎狻ransport 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

13、 for delivery else where in the cytoplasm.運輸小泡能夠將可運輸分子從內(nèi)質網(wǎng)運輸?shù)礁郀柣鶑秃象w上。在高爾基復合體中修飾，包裝后輸出細胞或傳遞到細胞質中的其他場所。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

14、for sugars and other molecules. Vacuoles in animal cells carry out phagocytosis (the intake of particulate matter) and pinocytosis (vacuolar drinking).細胞中的液泡好象是中空的，但實際上充滿了液體和可溶分子。最典型的液泡存在于植物細胞中，儲備水，糖以及其它分子。動物中的液泡起吞噬和胞飲作用。 A subset of vacuoles are the organelles known as lysosomes, which contain dige

15、stive enzymes (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.溶酶體是液泡亞單位，含有消化酶，降解大部分生物大分子。消化食物微粒和降解損傷的細胞殘片。Mitochondria are the sites of energy-yielding chemical reactions in all cells

16、. In addition, plant cells contain 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

17、they are the evolutionary descendants of what were once free-living prokaryotes.線粒體是細胞中化學產(chǎn)能的場所。另外，植物細胞中的質體在光合作用中利用光能產(chǎn)生碳水化合物，線粒體內(nèi)嵴上提供了很大的表面積并分布著產(chǎn)ATP酶。線粒體自我復制，并且可能是自由生活的原核生物在進化中形成的后代。There are two types of plastids: leucoplasts, which lack pigments and serve as storage sites for starch, proteins, and

18、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 includes stacks of membranes called grana, which are embedded in a matrix called the stroma.質體有兩種類型：

19、白色體，缺乏色素，是淀粉，蛋白質和油的儲備場所；色質體，含有色素。葉綠體是最重要的色質體，含有與光合作用有關的葉綠素。葉綠體的內(nèi)部結構是由多層膜形成的葉綠體基粒，其中包埋在基質中的基粒稱子座。The Cytoskeleton（細胞骨架）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 var

20、ious other organelles. A large portion 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 c

21、ells. Another main structural component 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. Mec

22、hanoenzymes such as myosin, dynein, and kinesin interact with the cytoskeletal filaments and tubules to generate forces that cause movements.所有的細胞都有細胞骨架，網(wǎng)絡結構的纖絲充滿了它所能觸及的全部空間并且對細胞器提供支持作用。細胞骨架大部分由微絲組成，微絲主要由可收縮的肌動蛋白組成。動植物細胞的許多種類型細胞內(nèi)運動與肌動蛋白有關。第二類蛋白是肌球蛋白，它與肌肉細胞的收縮有關。細胞骨架的另一個主要結構成分是微管，由球狀的微管蛋白組成，象腳手架一般維持細

23、胞的穩(wěn)定形態(tài)。細胞骨架的中間絲提供了細胞質伸縮動力。機械酶，例如，肌球蛋白，動力蛋白，驅動蛋白與微絲，微管相互作用產(chǎn)生動力而引起細胞運動。Cellular Movements（細胞運動 Although the cytoskeleton provides some stability穩(wěn)固 to cells, its microtubules英maikrutju:bju:l and filaments 絲狀物 and their associated proteins enable cells to move by creeping 爬行 or gliding 滑動. Such movement

24、s require a solid固體的 substrate to which the cell can adhere附著 and can be guided by the geometry dimitri  幾何形狀of the surface. Some cells also exhibit izibit 展覽 chemotaxis, kemtæksis趨藥性 the ability to move toward or away from the source of a diffusing 擴散 chemical.盡管細胞骨架提供了細胞的某些穩(wěn)定性，微絲，微管及相關蛋白

25、能使細胞爬行或滑動。這種運動需要固體基質依托并通過表面幾何形狀的改變而運動。某些細胞具備趨藥性，即趨向或逃離擴散開的化學源。Certain eukaryotic cells can swim freely in liquid environments, propelled by whiplike cilia sili纖毛or flagella 英fldel鞭毛. Both cilia and flagella have the same internal structure: nine doublets (pairs of microtubules) are arranged in a rin

26、g and extend the length of the cilium or flagellum, and two more microtubules run down the center of the ring. Every cilium or flagellum grows only from the cell surface where a basal body基體is located. Movement is based on the activities of tiny dynein動力蛋白 side arms that extend from one of the micro

27、tubules of each doublet成對的東西.某些真核細胞能在液體液體中自由運動，由纖毛或鞭毛推動。纖毛和鞭毛具有同樣的內(nèi)部結構：九個雙微管環(huán)形排列，縱向延伸，環(huán)中心是兩個或以上微管組成。纖毛或鞭毛從細胞表面的基體出生長，雙微管的動力蛋白臂從一側延伸到另一側而引起運動。Nutrients, proteins, and other materials within most plant cells are moved about via cytoplasmic streaming. The process occurs as myosin maiusin肌凝蛋白 proteins a

28、ttached to organelles 細胞器,小器官 push against microfilaments arrayed rei 展示throughout the cell. Microfilaments and microtubules are responsible for almost all major cytoplasmic movements. During cell division, microtubules of the spindle assembled 集合, 收集 from tubutin subunits near organelles called cen

29、trioles move the chromosomes. 大部分植物細胞的營養(yǎng)，蛋白質和其它物質由細胞質流運輸。這個過程是由于依附在細胞器上的肌球蛋白反推排列在細胞周圍的微絲形成的。絕大部分細胞質運動由微絲和微管完成。在細胞分裂期間，中心粒周圍的由微管蛋白亞基裝配形成的紡錘體微管移向染色體。Glossarycytoplasm （細）胞質The living contents of a cell bounded externally by the plasmalemma, including an aqueous ground substance (hyaloplasm, cell sap,

30、or cell matrix) containing organelles and various inclusions but excluding the nucleus and visible vacuoles.cytoskeleton 細胞骨架Of eukaryotic cells, an internal "skeleton". Its microtubules and other components structurally support the cell, organize and move its inteftial components. The cyt

31、oskeleton also helps free-living cells move through their environment. nucleus 細胞核，核(復數(shù) nuclei)The organelle of the eukaryote cell that contains the chromosomes and hence ultimately controls cellular activity and inheritance through the activity of the genetic material, DNAchromosome 染色體A DNA-histon

32、e thread residing in the nucleus of a cell. Each chromosome possesses two telomeres and a centromere, and some contain a nucleolus organizer. RNA proteins are invariably associated with the chromosome. nucleoid 擬核，類核，核質體The DNA-containing area of a prokaryote cell, analogous to the eukaryote nucleus

33、 but not membrane bounded.nucleoli 核仁( 單數(shù)nucleolus) Nuclear structures composed of completed or partially completed ribosomes and the specific parts of chromosomes that contain the infon-nation for their construction. nuclear envelope 核膜，核被膜A double membrane (two lipid bilayers and associated protei

34、ns) that is the outermost portion of a cell nucleus. ribosome 核糖體Small structures composed of two protein and ribonucleic acid subunits involved in the assembly of proteins from amino acids.polysome 多核糖體Of protein synthesis, several ribosomes all translating the same messenger RNA molecule,one after

35、 the other.endoplasmic reticulum 內(nèi)質網(wǎng)Folded membranes and tubes throughout the eukaryotic cell that provide a large surface upon which chemical activities take place.Golgi complex 高爾基復合體A stack of flattened, smooth, membranous sacs; the site of synthesis and packaging of certain molecules in eukaryot

36、ic cells.vacuole 液泡Storage container within the cytoplasm of a cell having a surrounding membrane.phagocytosis 吞噬作用The process by which the cell wraps around a particle and engulfs it.pinocytosis 胞飲作用The process by which a cell engulfs some molecules dissolved in waterlysosome 溶酶體A specialized organ

37、elle that holds a mixture of hydrolytic enzymes.mitochondrion 線粒體(復數(shù) mitochondria )A membranous organelle resembling a small bag with a larger bag resembling a small bag with a larger bag inside that is folded back on itself; serves as the site of aerobic cellular respiration.plastid 質體An organelle

38、present in all plants except bacteria, blue-green algae, and fungi; it is enclosed by two membranes (the envelope) and has various functionschloroplast 葉綠體A plastid in which photosynthesis is carried out. Chloroplasts occur in all photosynthetic organisms except photosynthetic bacteria blue-green al

39、gae.stroma 基質，子座（復數(shù) stromata）Region within a chloroplast that has no chlorophyll.microfilament 微絲，纖絲Long, fiberlike structures made of protein and found in cells, often in close association with the microtubules; provide structural support and enable movement.actin 肌動蛋白 A globular contractile protei

40、n. In muscle cells, actin interacts with another protein, myosin, to bring about contraction. myosin 'maiesin 肌球蛋白A protein that, with actin, constitutes the principal element of the contractile apparatus of muscle.microtubute 微管Small, hollow tubes of protein that function throughout the cytopla

41、sm to provide structural support and enable movement.tubulin 微管蛋白A protein that is the major constituent of microtubules.dynein 動力蛋白，動素A group of at least four distinct proteins found in the flagella and microtubules of eukaryotic cells and possessing ATPase activity. chemotaxis 趨化性A locomotory move

42、ment of an organism or cell in response to, and directed by, an directional stimulus.cilia 纖毛Numerous short, hairlike structures projecting from the cell surface that enable locomotion. flagella 鞭毛 (單數(shù)flagellum) Long, hairlike structures projecting from the cell surface that enable locomotion.basal

43、body 基體A body identical in structure to a centriole, found always at the base of a cilium or eukaryote flagellum.centriole 中心粒 An organelle located close to the nucleus in most animal and lower plant cells but absent from prokaryotes and higher plants.PhotosynthesisPhotosynthesis occurs only in the

44、chlorophyllchlorophyll葉綠素-containing cells of green plants, algae藻, and certain protists 原生生物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 cellula

45、r respiration. Whereas 然而 cellular細胞的 respiration 呼吸is highly exergonic吸收能量的 and releases energy, photosynthesis光合作用 requires energy and is highly endergonic.光合作用只發(fā)生在含有葉綠素的綠色植物細胞，海藻，某些原生動物和細菌之中?？傮w來說，這是一個將光能轉化成化學能，并將能量貯存在分子鍵中，從化學和動能學角度來看，它是細胞呼吸作用的對立面。細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過程。Photosynthesis start

46、s with CO2 and H2O as raw materials and proceeds through two sets of partial reactions. In the first set, called the light-dependent reactions, water molecules are split裂開 (oxidized), 02 is released, and ATP and NADPH are formed. These reactions must take place in the presence of 在面前 light energy. I

47、n the second set, called light-independent reactions, 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為原材料并經(jīng)歷兩步化學反應。第一步，稱光反應，水分子分解，氧分子釋放，ATP和NADPH形成。此反應需要光能的存在。第二步，稱暗反應，二

48、氧化碳被還原成碳水化合物，這步反應依賴電子載體NADPH以及第一步反應產(chǎn)生的ATP。Both sets of reactions take place in chloroplasts. Most of the enzymes and pigments 色素for the lightdependent reactions are embedded 深入的 內(nèi)含的in the thylakoid類囊體 membrane膜 隔膜 of chloroplasts 葉綠體. The dark reactions take place in the stroma.基質 兩步反應都發(fā)生在葉綠體中。光反應需要

49、的大部分酶和色素包埋在葉綠體的類囊體膜上。暗反應發(fā)生在基質中。How Light Energy Reaches Photosynthetic Cells（光合細胞如何吸收光能的）The energy in light photons in the visible part of the spectrum can be captured by biological molecules to do constructive work. The pigment chlorophyll in plant cells absorbs photons within a particular absorpt

50、ion spectrums statement of the amount of light absorbed by chlorophyll at different wavelengths. When light is absorbed it alters the arrangement of electrons in the absorbing molecule. The added energy of the photon boosts the energy condition of the molecule from a stable state to a less-stable ex

51、cited state. During the light-dependent reactions of photosynthesis, as the absorbing molecule returns to the ground state, the "excess" excitation energy is transmitted to other molecules and stored as chemical energy.生物分子能捕獲可見光譜中的光能。植物細胞中葉綠素在不同光波下吸收部分吸收光譜。在吸收分子中，光的作用使分子中的電子發(fā)生重排。光子的能量激活了分

52、子的能量狀態(tài)，使其從穩(wěn)定態(tài)進入不穩(wěn)定的激活態(tài)。All photosynthetic organisms contain various classes of chlorophylls and one or more carotenoid (accessory) pigments that also contribute to photosynthesis. Groups of pigment molecules called antenna complexes are present on thylakoids. Light striking any one of the pigment mo

53、lecules is funneled to a special chlorophyll a molecule, termed a reaction-center chlorophyll, which directly participates in photosynthesis. Most photosynthetic organisms possess two types of reaction-center chlorophylls, P680 and P700, each associated with an electron acceptor molecule and an elec

54、tron donor. These aggregations are known respectively as photosystem (P700) and photosystem (P680).所有的光合作用生物含有不同等級的葉綠素和一個或多個類胡蘿卜素（光合作用的輔助色素）。稱作天線復合體的色素分子群存在于類囊體中。激活色素分子的光能進入葉綠素反應中心，其直接參與光合作用。大部分光反應細胞器擁有兩套反應中心，P680和P700，每個光系統(tǒng)都含有一個電子受體和電子供體。這些集合體就是大家熟識的光合系統(tǒng)和光合系統(tǒng) 。The Light-Dependent Reaction: Converti

55、ng Solar Energy into Chemical-Bond Energy光反應：光能轉化成化學鍵能The photosystems of the light-dependent reactions are responsible for the packaging of light energy in the chemical compounds ATP and NADPH. This packaging takes place through a series of oxidation reduction reactions set in motion when light str

56、ikes the P680 reaction center in photosystem . In this initial event water molecules are cleaved, oxygen is released, and electrons are donated. These electrons are accepted first by plastoquinone and then by a series of carriers as they descend an electron transport chain. For each four electrons t

57、hat pass down the chain, two ATPs are formed. The last acceptor in the chain is the P700 reaction center of photosystem . At this point incoming photons boost the energy of the electrons, and they are accepted by ferredoxin. Ferredoxin is then reoxidized, and the coenzyme NADP+ is reduced to the NAD

58、PH. The ATP generated previously and the NADPH then take part in the light independent reactions.光反應的光系統(tǒng)將光能轉化成化學復合物ATP和NADPH。當光激活光系統(tǒng)的光反應中心時，通過一系列的氧化還原反應實現(xiàn)能量的傳遞。反應開始時，水被分解，氧被釋放并提供電子。電子首先傳遞給質體醌，然后通過一系列載體形成的電子傳遞鏈。每傳遞4個電子，形成2個ATP。最后一個受體存在于光反應系統(tǒng)的反應中心里。此處光子激活電子，電子傳遞給鐵氧還蛋白。鐵氧還蛋白再氧化，并且輔酶NADP+還原成NADPH。早期產(chǎn)生的ATP和NADPH進入暗反應。The production of ATP from the transport of electrons excited by light energy down