生物專業(yè)英語第三版蔣悟生課文翻譯精華整理

1、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 isbounded on the outside by the plasma membrane. Organelles are suspendedwithin it, supported by t. of the cytoskeleton. Dissolved inluid are nutrients

2、, 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，并由細胞膜包被。細胞器懸浮在其中，并由絲狀的細胞骨架支撐。細胞質 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 eukaryotic cell nucleus is the largest organelle and houses the genetic material (DNA) on chromosomes. (In prokaryotes

3、the hereditary material is found in the nucleoid.) The nucleus also contains one or two organelles-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

4、 envelope, but larger molecules such as mRNA and ribosomes must enter and exit via the pores.真核細胞的細胞核是最大的細胞器，為染色體上遺傳物質( DNA提供空間(原核生物遺傳物質存 在于擬核中)。細胞核含有一或二個核仁，在細胞分裂中發(fā)揮作用。一個穿孔的囊叫 核膜，將細胞核和其中內含物與細胞質分開，小分子物質可以自由通過核膜，但大 分子物質如mRN府口核糖體必須通過核孔進出核膜。All eukaryotic cells contain most of the various kinds of organ

5、elles, and each organelle performs a specialized function in the cell. Organelles described 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，每種細胞器在細胞中行使一項專門功能。 本節(jié)主要介紹核糖體、內質網、高爾基體系、液泡、溶酶

6、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 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

7、and one smaller subunit. During protein synthesis the two subunits move along a strand of mRNA, reading the geneticsequence coded in it and translatingthatsequence into protein.Several ribosomes maybecomeattached to a single mRNAstrand; such a combination is called a polysome. Most cellular proteins

8、 are manufactured on ribosomes in the cytoplasm. Exportable proteins and membrane proteins are usually made in association with the endoplasmic reticulum.細胞中核糖體的數量變化從幾百到幾千，核糖體數量如此之多反映了核 糖體是氨基酸組裝成蛋白質并被運出或在細胞過程中使用的位點這樣一個事實。完 整的核糖體由大亞基和小亞基組成。在蛋白質合成中兩個亞基沿mRNA移動，閱讀其中編碼的遺傳序列，將序列翻譯成蛋白質。一條mRNAt可能有多個核糖體，這種組合

9、稱多聚核糖體。大多數細胞中的蛋白質由細胞質中的核糖體（游離核糖體） 制造。運輸蛋白和膜蛋白通常由附著于內質網上的核糖體制造。The endoplasmic reticulum, a lacy array of membranous sacs, tubules, and vesicles, 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

10、 seems to be the source of the nuclear envelope after a cell divides.內質網是由膜狀囊、管和小泡等排列在一起，有粗面內質網和滑面內質網 兩種類型。兩種類型都與蛋白質的合成和運輸有關。粗面內質網上散布著多聚核糖 體，似乎也是細胞分裂后形成核膜的來源。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 en

11、doplasmic reticulum serve as compartments within the cell where specific products can be isolated and subsequently shunted to particular areas in or outside the cell.光滑內質網上無核糖體/光滑內質網上缺乏多聚核糖體，主要作用是脂肪和類 固醇的合成以及細胞內有毒物質的氧化。兩種內質網合成的產物在其中進行分流或 運輸到細胞外/這兩種類型的內質網都擔當細胞中的隔斷，致使特殊產物能夠分離并最終逃避到細胞內外的特定區(qū)域。Transport

12、vesicles may carry exportable molecules from the endoplasmic reticulum to another membranous organelle, the Golgi complex. Within theGolgi complex molecules are modified and packaged for export out of the cell or for delivery else where in the cytoplasm.運輸小泡能夠將可運輸分子從內質網運輸到高爾基復合體上。在高爾基復合體中修 飾，包裝后輸出細胞

13、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 for sugars and other molecules. Vacuoles in animal cells carry out phagocytosis (the in

14、take 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性分子。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(顆粒物的吸收)和胞飲作用。A subset of vacuoles are the organelles known as lysosomes, which contain digestive e(packaged in lysosomes in the Golgi complex) that can break down most

15、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(在高爾基體中的溶酶體中包裝而成)，能夠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/行使消化食物顆粒和分解損壞的細胞組件的作用。Mitochondria are the sites of energy-yielding chemical reactions in all cells. In addition, plant cells contain plastids

16、 that utilize light energytomanufacture 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 descendants of what

17、 were once free-living prokaryotes.線粒體是所有細胞中發(fā)生產能化學反應的場所。另外，植物細胞中的質體在光合作用中利用光能產生碳水化合物，線粒體內崎上提供了很大的表面積并分布著產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 oils; and chromoplasts, which contain p

18、igments.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：白色體，缺乏色素，是淀粉、蛋白質和油類的貯存場所；色質體，含有色素。葉綠 體是最

19、重要的色質體，含有與光合作用有關的葉綠素。葉綠體的內部結構是由多層 膜垛疊形成的葉綠體基粒，其中包埋在基質中的基粒稱子座。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 portion of the cytoskeleto

20、n 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 involvein the contraction of muscle cells. Another main structural component of the cytoskeleto

21、n 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 tensile strength to thecell cytoplasm. Mechanoenzymes such as myosin, dynein, and kinesin interact with the cyt

22、oskeletal filaments and tubules to generate forces that cause movements.所有的真核細胞都有細胞骨架，它是由細絲和管組成的回旋狀的網格， 似乎充滿了細胞中的所有空間并為其它各種細胞器提供了支撐作用。細胞骨架大部 分由線狀的微絲組成，微絲主要由可收縮的肌動蛋白組成。動物和植物細胞中多種 類型的細胞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組分是微管，由球形蛋白質一微管蛋白組成，象腳 手架那樣使細胞維持穩(wěn)定的形狀。細胞骨架的中間絲提供了細胞質伸縮動力。一些 動力酶如，肌球蛋白，動

23、力蛋白，驅動蛋白與微絲、微管相互作用產生動力而引起 細胞運動。Although the cytoskeleton provides somestability to cells, its microtubules and filaments and their associated proteins enable cells to moveby creeping or gliding . Such movements require a solid substrate to which the cell can adhere and can be guided by the geometry

24、of the surface. Some cells also exhibit chemotaxis, the ability to move toward or away from the source of a diffusing 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。某些細胞具備趨化性，即趨向或逃離擴散開的化學源。Certain eukaryotic cells can swim freely in liquid environments, propelledstructu

25、re: nineby whiplike cilia or flagella. Both cilia and flagella have the sameinternaldoublets (pairs of microtubules) are arranged in a ring and extend the length of the cilium or flagellum, and two more microtubules rundown the center of the ring. Every cilium or flagellum grows only from the cell s

26、urface 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.某些真核細胞能在液體中自由運動，由纖毛或鞭毛推動。纖毛和鞭毛具有同樣的內部結構：9個聯(lián)管（微管對）排列成環(huán)狀，沿纖毛或鞭毛縱向延 伸，環(huán)中心是兩個或兩個以上微管組成。纖毛或鞭毛從細胞表面的基體長出，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,

27、 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 movements. Du

28、ring cell division, microtubules of the spindle assembled from tubutin subunits near organelles called centrioles move the chromosomes.大部分植物細胞的營養(yǎng)物質、蛋白質和其它物質通過胞質流動進行運 動。這個過程是由于依附在細胞器上的肌球蛋白推動微絲在細胞中重排形成的。絕 大部分細胞質運動由微絲和微管完成。在細胞分裂過程中，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。Photosynthesis occurs only in the chlorop

29、hyllchlorophyll-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 inthe molecular bonds. From the point of view of chemistry and energetics, it is the opposite of cellular respiration. W

30、hereas cellular respiration is highly exergonic and releases energy, photosynthesis requires energy and is highly endergonic.光合作用只發(fā)生在綠色植物，海藻，某些原生動物和細菌等含有葉綠素的細胞中。總體來說，這是一個將光能轉化成化學能，并將能量貯存在化 學鍵中。從化學和能量學的角度來看，它是細胞呼吸作用的對立面。細胞呼吸作用 是高度放能的，而光合作用是需要能量并高吸能的過程。Photosynthesis starts with CO2and H20as raw mater

31、ials and 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 ATPand NADPH are formed. These reactions must take place in the presence of light energy. In the second set, called light-independ

32、ent reactions, CO2is reduced （via the addition of H atoms） to carbohydrate. These chemical events rely on the electron carrier NADP圖nd ATPgenerated by the first set of reactions. 光合作用以二氧化碳和水為原材料并經歷兩步化學反應。第一步反應稱為光反應， 水分子分解（氧化），放出氧氣，形成 ATP和NADPH這些反應必須有光能的存在才 能進行。第二步稱為非光依賴型反應（暗反應），二氧化碳被還原（通過加氫）成碳水化合物，這

33、步反應依賴于第一步反應產生的NADP儕口 ATP作為電子載體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.上兩步反應都發(fā)生在葉綠體中。光反應需要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。Th

34、e 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 absorption spectrums statement of the amount of light absorbed by chlorophyll at different wavelen

35、gths. When light is abt alters the arrangement of electrons in the absorbingmolecule. The added energy of the photon boosts the energyconditionof the molecule from a stable state to a less-stable excited state.During the light-dependent reactions of photosynthesis, as the absorbing molecule returns

36、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用于建設性的工作。植物細胞中葉綠素在不同光波下吸收特定 吸收光譜。當光線被吸收時，光的作用使分子中的電子發(fā)生重排/它改變了吸收分子的電子排列。由光子增加的能量推進分子的能量狀況從穩(wěn)定狀態(tài)(基態(tài))轉變?yōu)椴?穩(wěn)定的激發(fā)態(tài)。在光合作用的光反應過程中，吸收分子又回到基態(tài)，多余的激發(fā)能 傳遞到其它分子中，以化學能的形式儲存起來。All photosy

37、nthetic 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 molecules isfunneled to a special ch

38、lorophyll 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 electron donor. These aggregations are

39、known respectively as photosystemI (P700) and photosystem n (P680).所有的光合作用生物含有不同等級的葉綠 素和一種或多種類胡蘿卜素(輔助色素)，這些色素在光合作用中發(fā)揮作用。稱作天 線復合體的色素分子群存在于類囊體中。到達任何一個色素分子的光能匯集到稱為 反應中心葉綠素的特殊的葉綠素分子上，它直接參與光合作用。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)與電子受體分子和電子供體分子相 關聯(lián)。這些集合體就是大家熟識的光合系統(tǒng)I(P700)和光合系統(tǒng)n (P680) oThe photosystems of

40、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 strikes the P680 reaction center in photosystemn . Inthis initial event water

41、 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 that pass down the chain, two ATPs are formed. The last acceptor in the cha

42、in is the P700 reaction center of photosystemI .At this point incoming photons boost the energy of the electrons, and theyare accepted by ferredoxin. Ferredoxinis then reoxidized, and the coenzymeNADP+ is reduced to the NADPH. The ATP generated previously and the NADPHthen take part in the light ind

43、ependent 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)n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。/這一包裝過程從光線到達光合系統(tǒng)II的活性中心P680這一步驟開始，包括了一系列氧化還原反應反應。在第一個步驟中，水分子被 分解，放出氧氣，提供電子。電子首先傳遞給質體醍，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ATR鏈的最終受體是光合系統(tǒng)I的P700活 性中心。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前面產生的ATP和NADP進入暗反應。The prod

44、uction of ATPfrom the transport of electrons excited by light energy down an electron transport chain is termed photophosphorylation. The one-way flow of electrons through photosystems II and I is called noncyclic photophosphorylation; plants also derive additional ATP through cyclic photophosphoryl

45、ation, in which some electrons are shunted back through the electron transport chain between photosystems n and I .由光能激發(fā)產生的 電子沿電子傳遞鏈傳遞并產生ATP的過程稱為光合磷酸化。電子通過光合系統(tǒng)n流經光合系統(tǒng)I的電子路徑稱非循環(huán)式光合磷酸化；植物通過循環(huán)式光合磷酸化獲得 額外的atp,在這一過程中一些電子在光合系統(tǒng)I和n之間的電子傳遞鏈中回流。In the light-independent reactions of photosynthesis, which are d

46、riven byATP and NADPH, C02 is converted to carbohydrate. The reactions are also known as the Calvin-Benson cycle. Atmospheric CO2, is fixed as it reacts withribulose biphosphate (RuBP), a reaction that is catalyzed by the enzyme ribulose biphosphate carboxylThe reduction Of C02 to carbohydrate (fruc

47、tose diphosphate several more steps of the cycle. Finally, RUBP is regenerated so that the cycle may continue. 由ATP和NADP用區(qū)動的暗反應中，CO2$?；商妓衔?。即卡爾文-本森循環(huán)。在二磷酸核酮糖竣化酶的催化下，二磷酸核酮糖固 定空氣中的CO2 CO2通過循環(huán)中的幾步反應還原成為糖類(二磷酸果糖)，最終核酮糖二磷酸再生，這樣循環(huán)能夠持續(xù)進行。High levels of oxygen in plant cells can disrupt photosynthesis and

48、 can also cause photorespiration-an inefficient fun of the dark reactions in which 02 is fixed rather than C02 and no carbohydrate is produced.植物細胞中高濃度的氧氣能夠破壞光合作用，同時也能夠引起光呼吸，這是一種效率差的暗反應，02而不是CO2被固定，不產生糖類。Most plants are C3 plants; they experience decreased carbohydrate production under hot, dry cond

49、itions as a result of the effects of photorespiration.Among C4 plants, however, special leaf anatomy and a unique biochemical pathway enable the plant to thrive in and conditions. Thus C4 plants lessen photorespiration by carrying out photosynthesis only in cellsthat areinsulated from high levels of

50、 CO2. They also possess a novel mechanism for carbon fixation. 許多植物是C3植物，在高溫干旱條件下，由于光呼吸作用而使碳 水化合物的合成降低。而在大多數的C4植物中，由于葉脈的特殊構造和獨特的化學路徑使植物依然很茂盛。這樣C4植物并非在細胞中存在高濃度的CO2條件下才能進行光合作用，這是碳固定的一個新機制The cell nucleus is the main repository of genetic information. Within the nucleus are the chromosomes tightly coil

51、ed strands of DNA and clusters of associated proteins. Long stretches of the continuous DNA molecule wind around these clusters of proteins, or histones, forming beadlike complexes known as nucleosomes. More coiling and supercoiling produces a dense chromosome structure. Each long strand of DNA comb

52、ines with histones and nonhistone proteins to make up the substance chromatin.細胞核是貯藏遺傳信息的主要場所。DNA&繞成螺旋線以及相關的成簇蛋白質。DNA螺旋線纏繞成簇的組 蛋白形成珠鏈狀的核小體。這些螺旋或超螺旋形成致密的染色體組結構。每個長鏈 DNAf組蛋白和非組蛋白一起構成染色質。A pictorial display of an organisms chromosomes in the coiled, condensed state is known as a karyotype. Karyotype re

53、veal that in most cells all but sex chromosomes are present as two copies, referred to as homologous pairs. Non-sex chromosomesare called autoso.Organisms whose cells contain two sets of parental chromosomes are called diploid; those with cells containing a single set of parental chromosomes are cal

54、led haploid.以圖示方式展示出來的螺旋的、濃縮狀態(tài)有機體染色體，稱為染色體組型。除了性染色體外，大多數細 胞的染色體組成對出現(xiàn)，稱同源染色體對。非性染色體稱常染色體。生物細胞含有 兩套親本染色體的有機體稱為二倍體；含有單套染色體的有機體稱單倍體。The cell cycle is a regular sequence in which the cell grows, prepares for division,and divides to form two daughter cells, each of which then repeats the cycle. Such cycli

55、ng in effect makes single-celled organisms immortal. Many cellsin multicellular organisms, including animal muscle and nerve cells, either slow the cycle or break out of it altogether.細胞周期是一個有順序的過程：細胞生長、準備分裂、分裂形成兩個子細胞，子細胞再循環(huán)。此循環(huán)使得單細胞生 物永生。多細胞生物中的許多細胞，包括動物肌肉和神經細胞，能夠使細胞周期時 間延長或完全脫離細胞周期。The normal cell

56、 cycle consists of four phases. The first three include G1, the period of normal metabolism; S phase, during which normal synthesis of biological molecules continues, DNA is replicated, and histones are synthesized; and G2, a brief period of metabolism and additional growth.Toget G1, S, and G2 phase

57、s are called interphase. The fourth phase of thecell cycle is M phase, the period of mitosis, during which the replicatedchromosomes condense and move and the cell divides. It is believed thatproperties of the cell cytoplasm control the cell cycle, along with external stimulators and inhibitors such

58、 as chalones.正常的細胞周期包括四步。 前 3步包括G1（正常的代謝階段）；S期（持續(xù)進行生物分子的正常合成，DNA復制，組蛋白合成）；G2期（代謝和再次生長的短階段）。G1期、S期和G2期合起來稱為間 期。細胞周期的第四步為 M期（進行有絲分裂的階段），在這一階段，復制的染色 體濃縮、運動，細胞分裂。被認為是細胞質的特性和外部的刺激因子和抑制劑例如 抑素控制了細胞周期Biologists divide the mitotic cycle into four phases. At the beginning of prophase the chromosomes each cons

59、ist of two highly condensed chromatids attached to each other at a centromere. As prophase ends and metaphase begins, the condensed chromosomes become associated with the spindle. Eventually thein a plane (called the metaphase plate) at a rig spindle fibers. Next, during anaphase , the two sister ch

60、romatids of each chromosome split, and one from each pair is drawn toward each pole of the cell. During telophase nuclear envelopes begin to form around each set of chromosomes, and division of the cytoplasm takes place.生物學家將有絲分裂劃分為4個階段。分裂前期，每一條染色體包括兩條高度濃縮的染色單體，兩個染色單體通過著絲粒連接在一起。當前期結束時，分裂中期開始，濃縮的染色體與