Inside the Living Cell: Structure and
Function of Internal Cell Parts
Cytoplasm: The Dynamic, Mobile Factor y
细胞质：动力工厂细胞质：动力工厂
Most Most of of of the the the properties we properties we associate with life life are are are properties properties properties of of of the the cytoplasm. Much Much of of of the the
mass of a cell consists of this mifluid substance, which is bounded on the outside by the plasma membrane. Organelles Organelles are are are suspended suspended suspended within within within it, it, it, supported supported supported by by by the the the filamentous filamentous filamentous network network network of of of the 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，细胞器悬浮在其中，并由丝状的细胞骨架支撑。并由丝状的细胞骨架支撑。
并由丝状的细胞骨架支撑。细胞质中溶解了大量的营养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。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）（细胞核：信息中心）
The eukaryotic cell nucleus is the largest organelle and hous the genetic material (DNA) on chromosomes. (In prokaryotes the hereditary material is found in the nucleoid.) The nucleus also contains one or two organelles-the nucleoli-that play a role i n cell division. in cell division. A pore-perforated sac sac called called called the the nuclear nuclear envelope envelope parates parates the the the nucleus nucleus nucleus and and and its its its contents contents contents from from from the the the cytoplasm. 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。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）（细胞器：特殊的功能单位）
All All eukaryotic eukaryotic eukaryotic cells cells cells contain contain contain most most most of of of the the the various various various kinds kinds kinds of of of organelles, organelles, and and each each each organelle organelle performs a a specialized specialized function in the cell. Organelles described in this ction include ribosomes, ribosomes, the the the endoplasmic endoplasmic endoplasmic reticulum, reticulum, reticulum, the the the Golgi Golgi Golgi complex, complex, complex, vacuoles, vacuoles, vacuoles, lysosomes, lysosomes, lysosomes, mitochondria, 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。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 The number number number of of ribosomes within within a a a cell cell cell may may may range range range from from from a a a few few few hundred hundred hundred to to to many many many thousands. thousands.
This quantity reflects the fact that, ribosomes are the sites at which amino acids are asmbled into proteins for export or for u in cell process. A complete ribosome is comp
od of one larger and and one one one smaller smaller smaller subunit. subunit. During During protein protein protein synthesis synthesis synthesis the the the two two two subunits subunits subunits move move move along along along a a a strand strand strand of of mRNA, mRNA, "reading" "reading" "reading" the the the genetic genetic genetic quence quence quence coded coded coded in in in it it it and and and translating translating translating that that that quence quence quence into into into protein. 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 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。称多聚核糖体。大多数细胞蛋白是由细胞质中核糖体生产。大多数细胞蛋白是由细胞质中核糖体生产。大多数细胞蛋白是由细胞质中核糖体生产。输输出蛋白和膜蛋白通常与内质网有关。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 either rough rough rough (RER) (RER) (RER) or or or smooth smooth smooth (SER). (SER). Both Both types types types play play play roles roles roles in in in the the the synthesis synthesis synthesis and and and transport transport transport of of proteins. The RER, which is studded with polysomes, also ems 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 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 rve as compartments within the cell where specific products can be isolated and subquently shunted 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。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 el 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。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 rve as water rervoirs and storage sites for sugars and other molecules. V acuoles in animal cells carry out phagocytosis (the intake of particulate matter) and pinocytosis (vacuolar drinking).
盛情难却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。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 subt of vacuoles are the organelles known as lysosomes, which contain digestive enzyme
s (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。的细胞残片。
Mitochondria are are the
the the sites sites sites of of of energy-yielding energy-yielding energy-yielding chemical chemical chemical reactions reactions reactions in in in all all all cells. cells. In In addition, 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 ATP-generating enzymes enzymes enzymes are are are located. located. Mitochondria Mitochondria are lf-replicating, are lf-replicating, and and probably probably probably they they they are 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
怪物传说
碳水化合物，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线粒体内嵴上提供了很大的表面积并分布着产A TP 酶。线粒体自我复制，线粒体自我复制，并且并且可能是自由生活的原核生物在进化中形成的后代。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 rve as storage sites for starch, starch, proteins, proteins, proteins, and and and oils; oils; oils; and and and chromoplasts, chromoplasts, chromoplasts, which which which contain contain contain pigments. pigments. The The most most most important important chromoplasts chromoplasts are are chloroplasts-organelles that that contain contain contain the the the chlorophyll chlorophyll chlorophyll ud ud ud in in in photosynthesis. 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。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）（细胞骨架）
All All eukaryotic cells eukaryotic cells have have a cytoskeleton, which a cytoskeleton, which i s is is a convoluted a convoluted latticework latticework of of of filaments filaments filaments and and
tubules tubules that that that appears to fill appears to fill a ll all all available available available space space space in in in the cell the cell and and provides provides provides support support support for for for various various various other other organelles. A large portion of the cytoskeleton consists of threadlike microfilaments compod mainly mainly of of of the the the contractile contractile contractile protein protein actin. They They are are are involved involved in in many many many types types types of of of intracellular intracellular movements in plant and animal cells. A cond protein, m yosin, myosin, is involve in the contraction of muscle cells. Another main structural component of the cytoskeleton consists of
microtubules, which are compod 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 kinesin interact with the cytoskeletal filaments and tubules to generate forces that cau move
ments.
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。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（细胞运动
描写花开的诗句Although the cytoskeleton provides some stability 稳固 to cells, its microtubules
英[ˌmaikr əu ˈtju:bju:l ] and filaments 丝状物 and their associated proteins enable cells to move by creeping 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 ʒi ˈɔmitri ] 几何形状of the surface.
Some cells also exhibit [i ɡˈzibit ] 展览 chemotaxis, kem
əˈtæksis 趋药性 the ability to move toward or away from the source of a diffusing 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。向或逃离扩散开的化学源。
Certain eukaryotic cells can swim freely in liquid environments, propelled by whiplike cilia. 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 grows only from the cell surface where a
basal body基体is located. Movement is bad on the activities of tiny dynein
动力蛋白side arms that extend from one of the microtubules of each doublet
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
纤毛或鞭毛从细
秋田犬智商环中心是两个或以上微管组成。纤毛或鞭毛从细
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。
九个双微管环形排列，纵向延伸，
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。
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。
Nutrients, proteins, and other materials within most plant cells are moved about via cytoplasmic streaming. The process occurs as myosin
ˈmaiəusin肌凝蛋白proteins attached to organelles push against microfilaments arrayed
[əˈrei]展示throughout the cell. Microfilaments
and microtubules are responsible for almost all major
cytoplasmic movements. During cell division, microtubules of the spindle asmbled
来之不易的意思
集合, 收集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。
Photosynthesis
Photosynthesis occurs only in the chlorophyllchlorophyll叶绿素-containing cells of green
plants, algae藻, and certain protists 原生生物and bacteria. Overall, it is a process that converts
三星曲面屏From the point of view light energy into chemical energy that is stored in the molecular bonds.
Whereas 然而cellular细
of chemistry and energetics, it is the opposite of cellular respiration.
胞的respiration 呼吸is highly exergonic吸收能量的and releas energy, photosynthesis光合
作用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，
人生职业规划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 CO2and H2O as raw materials and proceeds through two ts of
partial reactions. In the first t, called the
water molecules are split
light-dependent reactions, w ater molecules are split
裂开(oxidized), 02 is relead, and A TP and NADPH are formed. The reactions must take 清炖羊肉的做法及配料
place in the prence of 在面前light energy. In the cond t, called light-independent
