Lession 3 Cell Structures and Functions 细胞结构和功能

Main contents  Introduction  Cell structures and functions  Assignment  New words and expressions

Introduction  Discovery of Cell （细胞发现） : The cell was first discovered by Robert Hooke in He examined very thin cork slices of oak bark （橡树树皮）.Robert Hooke Fig.1 R.Hooke,Microscope and slices of oak bark

 Cell theory( 细胞学说 ) （ ） :  Schleiden and Schwann ： All animals and plants are composed of cells.  In1855, Virchow proposed that "All living cells arise from pre-existing cells Fig.2 施莱登和施旺 Fig.3 R.C. 微耳和

 Cell theory is one of the foundations of biology biology  The current cell theory states: （ 1 ） All living things are composed of one or more cells. （ 2 ） The cell is the most basic unit of life. （ 3 ） All cells come from pre-existing cells. prokaryotic cell （原核细胞）  Cell types eukaryotic cell （真核细胞）

Why do we study cells ？  study cells to learn about （ 1 ） growth, （ 2 ） reproduction （繁殖）, （ 3 ） all other functions that living things perform. By learning about cells and how they function, you can learn about （ 4 ） all types of living things.

Cell structures （细胞结构）  cell wall ( 细胞壁 )  cell membrane （细胞膜）  cytoplasm （细胞质）  nucleus （细胞核） Cytosol 胞液 Organelle 细胞器 Endoplasmic reticulum Golgi apparatus Mitochondiron Chloroplast Lysosome Ribosome Centrosome Peroxisome Cytoskeleton Nucleolus Chromatin Stroma Nuclear envelope

Fig. 7.8 Fig.4 Structures of a plant cell

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.7 Fig.5 Structures of a animal cell

 （ 1 ） composition （组成）：  phospholipids （磷脂）（ hydrophilic end and hydrophobic end 亲水端和疏水端）  Proteins （蛋白质）.  Glycoprotein （糖蛋白），  Glycolipids （糖脂），  Steroid （类固醇） -cholecterol （胆固醇） 1. Cell membrane ( 细胞膜 )

Phospholipid bilayer Fig.6 液态镶嵌模型

 （ 2 ） Functions  Boundary （界限）  Selective permeable （选择透性）  Communiation mechanism （通讯）  Cell recognization （细胞识别）

 Diffusion 扩散  Passive transport Dialysis 透析  ( 被动运输 ) Osmosis 渗透  Facilitated diffusion 协助扩散  Active transport 主动运输  Exocytosis 外排作用  Endocytosis 内吞作用 （ 3 ） Mechnisms （机制）

 Diffusion: movement of molecules higher concentration place to lower con. place by concentration gradient 扩散 7

浓度梯度 8

 Dialysis: movement of wastes through membrane to lower concentration solution  Osmosis: water through membrane to higher concentration solution 透析作用 渗透作用 等渗液 高渗液 低渗液 9

Facilitated diffusion ( 协助扩散 ): carrier- assisted diffusion of molecules through membrane to lower concentration solution 载体 carrier 分子 molecules 细胞膜细胞膜 10

 Active transport( 主动运输 ): carrier- assisted diffusion through membrane from low concentration place to high concentration place  Exocytosis: wrap membrane around a particle and eliminate it  Endocytosis Phagocylosis ( 吞噬作用 ) pinocytosis ( 胞饮作用 ) 外排作用 内吞作用

主动运输 11

微生物 溶酶体 吞噬泡 外排作用 吞噬泡和 溶酶体融合 溶酶体内酶消化 12

2. Cytoplasm ( 细胞质 )  The semifluid substance inside the membrane is the cytosol ( 胞液 ).  In eukaryotic cells, the region between the nucleus and the plasma membrane is the cytoplasm, containing the organelles of specialized form and function.  In prokaryotic cells,all the material inside the plasma membrane is cytoplasm without organelles.

3.Organelles( 细胞器 )  Internal membranes compartmentalize （划分） the functions of a eukaryotic cell  These membranes also participate in metabolism as many enzymes are built into membranes.  The barriers created by membranes provide different local environments that facilitate specific metabolic functions. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3.1.Endoplasmic reticulum ( 内质网 )  Endoplasmic reticulum (ER) is a series of interconnected membranous tubes and channels in the cytoplasm. There are two kinds of ER that differ in structure and function, Smooth ER( 滑面内质网 ) and Rough ER ( 粗面内质网 ).

 Smooth ER looks smooth because it lacks ribosomes.  Rough ER looks rough because ribosomes are attached to the outside, including the outside of the nuclear envelope. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 13

Functions of Smooth ER ( 滑面内质网功能 ) （ 1 ） synthesize lipids ( 合成脂类 ), including oils, phospholipids, and steroids such as the sex hormones of vertebrates and adrenal steroids. （ 2 ） Transport lipids to Golgi apparatus ( 运输脂类到高尔基体 ) Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

（ 3 ） detoxify drugs and poisons ( 解毒 ) Other enzymes in the smooth ER of the liver  These include alcohol  Frequent exposure leads to proliferation of smooth ER, increasing tolerance to the target and other drugs. （ 4 ） Muscle cells are rich in enzymes that pump calcium ions ( 钙离子泵 ) Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

 When nerve impulse stimulates a muscle cell, calcium rushes from the ER into the cytosol, triggering contraction.  These enzymes then pump the calcium back, readying the cell for the next stimulation.

Functions of Rough ER ( 粗面内质网功能 ) （ 1 ） Produce proteins ( 合成蛋白质 ) Rough ER is especially abundant in those cells that secrete proteins. These secretory proteins are packaged in transport vesicles that carry them to their next stage. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

 （ 2 ） manufacture membranes( 合成膜 )  Membrane bound proteins are synthesized directly into the membrane.  Enzymes in the rough ER also synthesize phospholipids from precursors in the cytosol.  As the ER membrane expands, parts can be transferred as transport vesicles to other components of the endomembrane system. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3.2.Lysosome ( 溶酶体 )  Definition ( 定义 ) :vesicles containing hydrolytic enzymes from the outside surfaces of Golgi apparatus;  Functions Break down food particles ( 分解食物颗粒 ) Destruct engulfed microbes ( 降解吞噬微生物 ) Take part in development ( 参与发育 ) 功能

Examples  1.acrosome ( 顶体 ):a large and specific lysosome in animal sperm containing 透明质酸酶 (Hyaluronidase )  2.Syndactylism ( 并趾 / 指现象 )  3.Silicosis ( 硅肺病, 矽肺 ): 硅 silicon 使溶酶 体膜破裂, 释放酶, 细胞死亡, 使成纤维细胞 胶原纤维结沉积.

Fig.16 精子穿过透明带 ●哺乳动物的卵子，被一层糖蛋白外衣即细胞的外基质包裹着。当精 子到达卵子的质膜之前，必须穿过这一层透明带，这对精子来说， 是一个考验。如果精子存在质量问题，往往被拒之门外。 ●在排卵期，透明带外边还有卵丘包围，而卵丘由卵丘细胞和细胞外 基质组成。细胞外基质的主要成分是聚合化的透明质酸。只有经过 顶体反应的精子才可能通过透明带，并与卵质膜融合。 Fig. 13

( 并趾 / 指现象 ) 遗传病 Fig. 17

肺里黏满了石粉，石粉让 肺泡板结成一团团、一条 条的硬块，鲜红、柔软的 肺失去了弹性， X 片上呈 现一片死灰般的蛛网斑 点 …… 它的主人现在气喘吁吁， 胸中火辣辣的痛，不能弯 腰，没法多走路，年纪轻 轻，手无缚鸡之力。他得 了矽肺，一种不治之症， 职业病诊断书给他判了 “ 死 刑 ” ，缓期执行，他离肺结 核、肺部感染，或者肺源 性心脏病很近，一场轻微 的感冒都可能致命。 Fig. 18 广东矽肺病患者

蝌蚪 (tadpole) 青蛙 (frog) Fig. 19 Indirect Development

 Mitochondria and chloroplasts are the organelles that convert energy to forms that cells can use for work Mitochondria ( 线粒体 ) Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

 Almost all eukaryotic cells have mitochondria.  There may be one very large mitochondrion or hundreds to thousands in individual cell. 每个人类 细胞平均一万个线粒体.  The number of mitochondria is correlated with aerobic metabolic activity.  A typical mitochondrion is 1-10 microns long.  Mitochondria are quite dynamic: moving, changing shape, and dividing. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

 Structure ( 结构 )  Composition ( 组成 ) - composed of modified double unit membrane. protein( 蛋白质 ) lipid( 脂类 ) nucleic acids( 核酸 ) salt ( 无机盐 ) cofactors( 辅助因子, 如 NAD+ ) 内外膜 Inner and outer membrane 嵴 Cristae 基质 Matrix

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 20

 Mitochondria have a smooth outer membrane and a highly infolded inner membrane, the cristae.  This creates a fluid-filled space between them.  The cristae present ample surface area for the enzymes that synthesize ATP.  The inner membrane encloses a fluid-filled space with DNA, ribosomes, and enzymes. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

 Function( 功能 ) - site of cellular respiration  the process of the release of chemical energy and carbon dioxide from food molecules, which requires the participation of oxygen molecules ( 在线粒体中氧化食物糖, 释放能量 和二氧化碳的过程 )  Glucose + Oxygen > Carbon Dioxide + Water + Energy (ATP)  In fact, Mitochondria can generate ATP from the catabolism of sugars, fats, and other fuels in the presence of oxygen. 呼吸作用场所

3.4.Chloroplast ( 叶绿体 )  Chloroplasts are membranous, saclike, energy-converting organelle containing green pigments-----chlorophylls

Chloroplast structure ( 叶绿体结构 ) Meso- phyll Vein Stomata Leaf cross sectionMesophyll cell Chloroplast Inner membrane Outer membrane Grana Stroma Thylakoid space 叶横切面 叶肉细胞 叶绿体 内外 膜

外膜内膜 基质 基粒 Thylakoid 类囊体

 Composition( 组成 ): the same as the mitochondrial( 同线粒体成分 )  Function( 功能 ) : the site of photosynthesis found in plants and eukaryotic algae( 植物和真 核藻类的光合作用场所 ).  photosynthesis : The process of the conversion of solar energy to chemical energy and the synthesis of new organic compounds from CO 2 and H 2 O,in which oxygen is released.

 6CO 2 + 6H 2 O C 6 H 12 O6 +6O 2 + ATP  光合作用 : 叶绿体把光能转变为化学能、把二氧 化碳和水转变为糖, 释放氧气的作用 Light 光能 Chloroplast 叶绿体

3.5.Nucleus ( 细胞核） The nucleus consists of nuclear envelope 核膜 nucleolus 核仁 chromatin 染色质 (Chromosome 染色体 ) nucleoplasm 核质（基质）

（ 1 ） chromatin( 染色质 )  Within the nucleus, the DNA and associated proteins are organized into fibrous chromatin( 染色质 ), which are more heavily stained than other parts by certain dyes, which contains two strands of helical DNA and its associated proteins, called histones （组蛋白）. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

（ 2 ） Chromosome ( 染色体 )  when the cell prepares to divide,  the chromatin fibers coil up to be  seen as shorter, denser, separate structures, chromosomes ( 染色体 ), composed of chromatin. During cell division, the DNA becomes tightly wound around the histones to form structures called nucleosomes （核小体）, which are further coiled and packaged into the highly condensed chromosome.

 A typical human cell has 46 chromosomes, but sex cells (eggs and sperm) have only 23 chromosomes.

 The essential part of a chromosome is a single very long strand of DNA that contains all the genetic information for creating and running the organism.  At different times, histones cause the DNA to be spread out like spaghetti in a bowl, or tightly condensed into the X-shaped chromosomes in the microscope.  Each chromosome has a central constricted region called a centromere that serves as an attachment point for the machinery of mitosis.

 Fixed in number within the nuclei of all body cells  Thread-like structure  Carry genetic materials (determine the characteristics of the organism)  No. of chromosomes in the body cells of organisms of the same species is always the same  Always occur in pairs (homologous chromosomes)

 Non-dividing cells  Chromosomes cannot be distinguished under the microscope  Very fine extended threads  Chromatins  Dividing cells  Become much shorter and thicker  Can be seen under the microscope  Darkly stained threads (after treatment)

 Vesicles and vacuoles (larger versions) are membrane-bound sacs with varied functions in cell maintenance.  Food vacuoles, from phagocytosis, fuse with lysosomes.  Contractile vacuoles, found in freshwater protists, pump excess water out of the cell.  Central vacuoles are found in many mature plant cells. 3.6.Vacuoles Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3.7. Golgi apparatus( 高尔基体 )  （ 1 ） Structure ( 结构 ): The Golgi apparatus consists of flattened membranous sacs( 囊 ) - looking like a stack of pancakes ( 煎饼 ).  The membrane of each cisterna ( 嵴 )separates its internal space from the cytosol Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 14

 （ 2 ） Function( 功能 ) The Golgi is a center of manufacturing, warehousing, sorting, and shipping cell products.  Synthesize and package molecules ( 合成与包装分子 )  Transport molecules such as carbohydrates, glycoprotein, insulin and enzymes( 运输 ).  Convert hydrolytic enzymes from inactive to active forms ( 转化 ).

Prokaryotes vs. Eukaryotes

Assignments  Which important structures does an eukaryotic cell have?  Main organelles and their functions in an eukaryotic cell

New words and expressions  Plasma membrane (Cytoplasma) 细胞膜  Cytosol 细胞液  Organelle 细胞器  Endoplasmic reticulum (ER) 内质网  Golgi complex (apparatus) 高尔基体  Mitochondiron 线粒体  Chloroplast 叶绿体  Lysosome 溶酶体

 Ribosome 核糖体  Centrosome 中心体  Centriole 中心粒  Peroxisome 过氧物酶体  Cytoskeleton 细胞骨架 (microfilament 微丝, intermediate filament 中等纤维, microtubule 微管 )  Vacuole 液泡  Flagellum (pl.flagella) 鞭毛

 Nucleus (pl.nuclei) 细胞核  Nucleolus (pl.nucleoli) 核仁  Nucleosome 核小体  Chromatin 染色质  Chromatid 染色单体  Chromosome 染色体  Nucleoid 拟核  Stroma (pl. stromata) 基质  Phagocytosis 噬菌作用

Cytoskeleton( 细胞骨架 ) 微管 微丝中等纤维

Functions of cytoskeleton ( 细胞骨架的功能 )  Provide cells with shape, support, the ability to move about the environment  Transport materials  Take part in mitosis and meiosis  And so on