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SECTION 1细胞的大小和分类SECTION 1细胞的大小和分类 SECTION 1 细胞的大小和分类 (The size and classification of cell) 1.1 细胞的大小 自然界中各种生物的细胞大小不一。生物个体大其细胞不一定就大。自然界中最小的细胞是属于细菌类的支原体,直径只有100nm。 鸟类的细胞最大,神经细胞可达1m以上。这些形态结构和大小是与其机能相适应的。 1.2 分类 按照细胞的结构和遗传物质在细胞内的分布,生命有机体可大致划分为:原核生物( Prokaryotes )和真核生物( Euka...

SECTION 1细胞的大小和分类
SECTION 1细胞的大小和分类 SECTION 1 细胞的大小和分类 (The size and classification of cell) 1.1 细胞的大小 自然界中各种生物的细胞大小不一。生物个体大其细胞不一定就大。自然界中最小的细胞是属于细菌类的支原体,直径只有100nm。 鸟类的细胞最大,神经细胞可达1m以上。这些形态结构和大小是与其机能相适应的。 1.2 分类 按照细胞的结构和遗传物质在细胞内的分布,生命有机体可大致划分为:原核生物( Prokaryotes )和真核生物( Eukaryotes ) 另外,有生命特征的还有病毒(Virus)和朊病毒(Prion)。 2. 细胞的结构与各组分的功能 2.1 原核生物( Prokaryotes ) 2.1.1大肠杆菌(Escherichia coli E.coli)的结构 : 1885 Theodor Escherich (德国)发现 原命名为 Bacterium coli将其属名改为 Escherichia 是为了纪念发现者。其结构为: 1 (1) 毛(Flagella) 能做旋转运动从而使细菌运动. (2)纤毛(Pili): 没有运动功能。其作用是使细菌相互附着成为菌落。而成为菌落的细菌才能使宿主发病。 (3) 胞壁(Cell WALL): 不含纤维素。主要成分是乙酰胞 壁酸(N-ace-tylmuramic acid)的肽聚糖。其功能是一 种屏蔽作用,以避免细胞在渗透压与细胞内显著不同 的环境中膨胀或收缩。 (4) 质膜(Plasma membrane):即细胞膜。为脂质双层的 蛋白质镶嵌结构。其功能是选择透过性和呼吸。 (5) 核糖体(Ribosomes):蛋白质合成场所。合成后蛋白 质的趋向是由信号肽(Signal piptide)决定的。 ,6,质粒(Plasmid): 独立于染色体外的,能自主复制且 稳定遗传的遗传因子。是一种环状的双链DNA分子。 存在于细菌、放线菌、真菌以及一些动植物细胞中, 在细菌细胞中最多。在现代分子生物学研究中具有重 要作用(Vector)。质粒也携带许多基因,如:抗生素 抗性基因。 2 (7) 类核体(Nucleoid):位于细菌特定区域内(通常在两 端且靠近质膜,因而易变)。含有少量RNA和非组蛋 白(Nonhistone protein)。类核中,染色体DNA成分占 80,,其余为RNA和蛋白质对数生长期的E.coli (2, 64个类核). DNA. 4.6 x 10bp的基因组DNA 与多种 DNA结合蛋白质组装成E.coli的染色体.基因组DNA为 双链环状,总长度为1100,1400μm,1400个基因都 已定位其功能是储存和传递信息。 2.1.2 大肠杆菌在实际工作中的重要性 经常被当作是所有生物的原型(archetype)a、在实验室中容易操作;b、生长迅速,要求营养物质简单,能进行很多生理生化过程;c、其有性生殖的存在使得遗传学的研究成为可能(遗传杂交、遗传性状、存在性状 )d、能够供应细菌病毒的生长,使病毒的本性即病毒扩增的深入研究成为可能。 3 2.2.2 真核细胞和原核细胞的区别: 原核细胞 真核细胞 核膜 无核膜,故无成形的有核膜 细胞核 核仁 无 有 染色质 只有裸露的DNA,无染有染色质 色质 细胞壁 由粘多糖构成 由纤维素构成 细胞器 没有内质网、高尔基细胞器较多 体、线粒体、叶绿体 2.2.3 动物细胞和植物细胞的区别:如下图: 4 主要区别:动物细胞:有Contriole;植物细胞有:细胞 壁(Cell wall)、叶绿体(Chloroplast)、脂肪滴(Vacuole)。 2.2.4 亚细胞器及其的功能(Subcellular organelles and its funaction) (1)细胞核(Nuclei):细胞的控制中心 (The membrane-bound nucleus contains the bulk of the cellular DNA in multiple chromosomes. Transcription of this DNA and processing of the RNA occurs here. Nucleoli are contained within the nucleus.) (2 ) 线粒体(Mitochondria) 5 Function and structure: ATP and breath (3) 叶绿体(Chloroplast) 叶绿体(Chloroplast):进行光合作用 2.4 内质网(ER) Rough and smooth ER, ribosome 内质网(Endoplasmic Reticulum,ER)又分为:Rough ER (有ribosome 附着, 合成并运送蛋白质)and smooth ER(合 成脂肪,激素,解毒等) 2.5 Golgi apparatus 高尔基复合体(Golgi apparatus):蛋白质合成后进行加 工、修饰、分检并引导其到特定位置 6 Golgi apparatus is a major site for sorting and modifications of proteins and lipids. After proteins are sorted at rough ER, they are enclosed in transport vesicles and carried to the Golgi apparatus. Some proteins could be modified into glycoproteins and then transported to other destinations 2.6 微体(Microbodies) 微体(Microbodies):分为溶菌酶(lysosomes,将来自 损伤细胞器的大分子分解并重新利用);过氧化物酶 (peroxisomes,将过氧化氢分解)和乙醛酸循环体 (glyoxysomes ,将脂类转变为糖)) The lysosomes contain degradative, hydrolytic enzymes; the peroxisomes (过氧化物酶体)contain enzymes which destroy certain potentially dangerous free radicals and hydrogen peroxide; the glyoxysomes (乙醛酸循环体)of plants carry out the reactions of the glyoxylate cycle. Organelle isolation After disruption of the plasma membrane, the subcellular organelles can be separated from each other and purified by a combination of differential centrifugation and density gradient centrifugation. Purity can be assayed by measuring organelle-specific enzymes. 2.2.4 动物细胞三维模式图: 7 3. 真核生物的染色体 人有23对染色体,其中两条为性染色体,女性成对(XX),男性为(XY),其中Y较小,信息载荷(Information loading)也小,没有配对,为孤单染色体,复制时为镜像复制。 4 核生物的染色体的装配 装配程序: 染色体的基本单位核小体。核小体由DNA和组蛋白共同构成。组蛋白分子共有五种,分别称为H,HA,HB,H和H12234共同构成了核小体的核心,称为组蛋白八聚体(又称核心组蛋白)。DNA双螺旋分子缠绕在这一核心上构成了核小体的核心颗粒(core particle)。核小体的核心颗粒之间再由DNA (约60个碱基对,bp)和组蛋白H构成的连接区连接起1 来形成串珠样的结构(图3-10)。在此基础上,核小体又进一步旋转折叠,形成纤维状结构及襟状结构、最后形成棒状的染色体,将近l m长的DNA分子容纳于直径只有数微米的细 8 胞核中。 DNA双螺旋分子?组蛋白八聚体?DNA双螺旋分子缠绕(核心颗粒)?串珠样的结构?维状结构及襟状结构?棒状的染色体 过程模式为: 真核DNA,组蛋白形成核小体,核小体再进一步折叠压积形成染色质(chromatin)。 4.1 核小体(Nuclearsome)的形成 染色体结构的第一个层次,构成染色质的基本结构单位 . 146bpDNA , 组蛋白八聚体?核小体的核心颗粒,直径约10nm. (1) 组蛋白八聚体(Histone octamer ) 9 H2A与H2B、H3与H4的亲和力强,通过C端的疏水氨基酸结合. 两个H3、H4先形成四聚体,再结合两个H2A和H2B的异二聚体形成 组蛋白八聚体 .如图 (2) 146bpDNA缠绕组蛋白八聚体 组蛋白八聚体 146bp的核心DNA 146bp的核心DNA在组蛋白八聚体上盘绕1.8(1又3/4) 10 圈(3) 组蛋白H1把核小体“封锁”起来 4.2 染色体结构的形成 首先,若干个核小体形成念珠状结构 。 其次,30nm纤丝的构成,,染色质结构的第二层次。 11 最终形成体内存在状态: 4.3 着丝粒(centromere或中心粒)和端粒(telomere)存在于有丝分裂中期的染色体,如图 Centromere 着丝粒 30nm 纤丝环 Nuclear matrix 核基质姊妹染色单体 Chromatid 染色单体 12 端粒(Telomere ) a、真核染色体线性DNA末端的 特殊DNA序列;b、有数百个拷贝的短的正向重复序列 ,且 总是3’端富含G。如:人体内c、复制靠5’-TTAGGG-3’; 端粒酶( telomerase ,核蛋白)来完成 ,不同于正常DNA 的复制;d、端粒DNA形成特殊的二级结构(G四联体形成四 链结构)以使染色体末端免遭降解。 5. 生物大分子(Macromolecules) 大体上可分为五类: 蛋白质(Protein) (next chapter) 核酸(Nucleic acids) (next chapter) 多糖(Polysaccharides) 脂类(Lipids) 复合大分子(Complex macromolecules) 自己复习) (protein and nucleic acids (next chapter) ,polysaccharides ,lipids ,complex macromolecules) 5.1 多糖(Polysaccharides) alpha-Amylose(直链淀粉) and cellulose(纤维素) are polymers of glucose linked alpha(1-4) and beta(1-4) respectively. Starch(淀粉), a storage form of glucose found in plants, contains alpha-amylose together with the alpha(1-6)branched polymer amylopectin. Glucose(糖原) is stored as glycogen in animals. Chitin(几丁质), a polymer of N-acetylglucosamine, is found in fungal cell walls and arthropod exoskeletons. 13 Mucopolysaccharides are important components of connective tissue. 5.2 Lipids , Triglycerides(甘油三酯) containing saturated (饱和)and unsaturated fatty acids are the major storage lipids of animals and plants respectively. Structural differences between the two types of fatty acid result in animal triglycerides being solid and plant triglycerides (oils) liquid. Phospholipids(磷脂) and sphingolipids(鞘脂) have polar(极性) groups in addition to the fatty acid components, and are important constituents of all cell membranes. Lipids: individual lipids are not strictly macromolecules, large lipid molecules are built up from small monomeric(单体) units and involved in many macromolecule assembly Glycerides(甘油脂) consisting one , two or three long-chain fatty acids esterified to a molecule of glycerol Triglycerides : consisting three long-chain fatty acids esterified(酯化) to a molecule of glycerol(甘油) Phospholipid: glycerol esterified to two fatty acids and phosphoric acid Sphingomyelin(磷酸酯胆碱). 5.3 Complex macromolecules Nucleoproteins contain both nucleic acid and protein, as in the enzymes telomerase and ribonuclease P(核糖核酸酶 P). Glycoproteins and proteoglycans (mucoproteins) are proteins with covalently(共价) attached carbohydrate and are generally found on extracellular surfaces and in extracellular spaces. Lipid-linked proteins and lipoproteins have lipid and 14 protein components attached covalently or noncovalently respectively. Glycolipids have both lipid and carbohydrate parts. Mixed macromolecular complexes such as these provide a wider range of functions than the component parts. Glycoproteins: containing both protein and carbohydrate, covalent attachment . They are very important in mediating cell-cell recognition. Proteoglycans(蛋白多糖): protein and mucopolysaccharide(粘多糖),bacterial cell walls and in the extracellular space in connective tissue(结缔组织). Lipid-linked proteins: covalently(共价) attached, the lipid moiety serves to anchor proteins in membranes and promotes protein-protein interaction. Lipoproteins: proteins and lipids are linked noncovalently (非共价) apolipoproteins ,particles of triglycerides and cholesterol coated with a layer of phospholipids, cholesterol and protein (polar amino acids of the protein make the particles soluble). glycolipids: lipids and carbohydrates are covalently linked. For exapmle,cerebrosides and gangliosides, abundant in brain 15 and nerve cells 6. Large macromolecular Assemblies 6.1 Protein complexes: , The eukaryotic cytoskeleton(细胞骨架) consists of various protein complexes: microtubules (made of tubulin), microfilaments (made of actin and myosin) and intermediate filaments (containing various proteins). These organize the shape and movement of cells and subcellular organelles. Cilia and flagella are also composed of microtubules complexed with dynein and nexin. protein complexes Schematic diagram showing the (a) cross-sectional and (b) surface pattern of tubulin a and b subunits in a microtubule 6.2 Nucleoprotein: Bacterial 70S ribosomes comprise a large 50S subunit, with 23S and 5S RNA molecules and 31 proteins, and a small 30S subunit, with a 16S RNA molecule and 21 proteins. Eukaryotic 80S ribosomes have 60S (28S, 5.8S and 5S RNAs) and 40S(18S RNA)subunits. Chromatin contains DNA 16 and the basic histone proteins. Viruses are also nucleoprotein complexes. Nulceoprotein: associations of nucleic acids and protein Ribosome: consisting of ribosomal proteins and rRNA structural function catalytic function 6.3生物膜(Membrane):由磷脂(phospholipids) 和鞘脂 (sphingolipids)组成的脂质双层(Lipid bilayer). 极性基团在外 侧,疏水长链在内侧.蛋白质镶嵌其中. Membrane phospholipids(磷脂) and sphingolipids(鞘脂) form bilayers with the polar groups on the exterior surfaces and the hydrocarbon chains in the interior. Membrane proteins may be peripheral(外周) or integral(镶嵌) and act as receptors, enzymes, transporters or mediators of cellular interactions 17 外周膜蛋白(Peripheral protein):松弛地结合在膜的外 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf , 易于流动,多起酶(Enzymes)的作用. 镶嵌膜蛋白(Integral protein) :部分或全部包埋在膜中, 不易流动。可作为激素或神经递质等信号分子的受体 (Receptors)。 跨膜蛋白(Transmembrane protein):贯穿细胞膜,有 变构功能,作为载体(Transporters)运输小分子、极性离子 等。 糖蛋白(Glycoprotein):常以integral protein形式存在, 糖基化位点在外表,作为细胞间相互作用的介质 (Mediators of cellular interactions ) Schematic diagram of typical membrane proteins in a biological membrane. The phospholipid bilayer, the basic structure of all cellular membranes, consists of two leaflets of phospholipid molecules whose fatty acyl tails form the hydrophobic interior of the bilayer; their polar, hydrophilic head groups line both surfaces. Most integral proteins span the bilayer as shown; a few are tethered to one leaflet by a covalently attached lipid anchor group. Peripheral proteins are primarily associated with the membrane by specific protein-protein interactions. Oligosaccharides bind mainly to membrane proteins; however, some bind to lipids, forming glycolipids. 18 Freeze fracturing can separate the two phospholipid leaflets that form every cellular membrane. (a) A preparation of cells or tissues is quickly frozen in liquid nitrogen at 196 ?C, which instantly immobilizes cell components. (b) The block of frozen cells is fractured with a sharp blow from a cold knife. The fracture plane is irregular, often between the leaflets of the plasma or an organelle membrane. (c) Membrane proteins and particles remain bound to one leaflet or the other, as illustrated in the expanded view of a fractured membrane 19 Faces of cellular membranes. For organelles enclosed in two phospholipid membranes (e.g., the nucleus, chloroplast, mitochondrion), the exoplasmic faces (red) border the space between the inner and outer membranes. Chloroplasts also contain a stack of internal thylakoid membranes; the exoplasmic face of these membranes line the thylakoid lumen. The watery interior of cells is surrounded by the plasma membrane, a two-layered shell of phospholipids. Cholesterol molecules provide some rigidity to the fatty layer. The phospholipid molecules are oriented with their fatty chains facing inward and their water-seeking head groups (red spheres) facing outward. Thus both sides of the membrane are lined by head groups, mainly charged phosphates, adjacent to the watery spaces inside and outside the cell. In actuality, the interior space 20 is much larger relative to the volume of lipid. All biological membranes have the same basic phospholipid bilayer structure A space-filling model of a typical phospholipid bilayer. The hydrophobic interior is generated by the fatty acyl side chains. Some of these chains have bends caused by doublebonds. The different polar head groups all lie on the outer, aqueous surface of the bilayer 21 作业 一、名词解释: Nucleoprotein,microbodies. 二、选择 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 : 1(分泌蛋白的糖基化作用发生在( )中。 (a)线粒体 (b)过氧化物酶体 (c)内质网 (d)核 2(以下哪一个是核蛋白? ( ) (a)角蛋白 (b)染色质 (c)组蛋白 (d)蛋白聚糖 3(以下哪一个不是多糖? ( ) (a)几丁质 (b)支链淀粉 (c)黏多糖 (d)甘油 4(跨膜蛋白( )。 (a)将两个脂双层连接一起 (b)有胞内和胞外结构域 (c)完全包埋在膜内 (d)很容易从膜上去除下来 5.生物膜流动性的最好证据来自( ) A.冰冻蚀刻实验 B.细胞融合实验 C.脂类的流动性 D.液态镶嵌结构模型 E.X-线衍射 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 6.细胞膜的主动运输作用与被动运输作用不同,这是因为:( ) A.需要能量,但不需要运输蛋白 B.主要依赖扩散作用与渗透作用 C.需要载体而不需要能量 D.在磷酸酯键形成时,需要能量 E.与胞饮作用有关 22
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