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  • 其他细胞结构----高级

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    How are chromosomes separated during cell division?
    ::细胞分裂期间染色体是如何分离的?

    They are pulled apart by spindle fibers. The fibers are made of microtubules and are organized by the centrioles . Two pairs of centrioles are seen on opposite sides of the during prophase , the first phase of .
    ::纤维由微孔组成,由中子组组成。在前期,即第一阶段,两对中子组在对面。

    Centrioles
    ::单列

    Centrioles are rod-like structures made of short microtubules. Though they are found in most eukaryotic cells , centrioles are absent in some plants and most .
    ::Centrioles是用短小微泡制成的棒状结构。 虽然在大部分的eukaryaty细胞中都发现了这种结构,但在某些植物和大多数植物中却缺少centrios。

    Nine groups of three microtubules (nine triplets) make up each centriole. The nine triplets are arranged in a cartwheel-like orientation. Two perpendicularly placed centrioles make up the centrosome . Centrioles are very important in cellular division, where they arrange the mitotic spindles that pull the apart during mitosis. The position of the centriole determines the position of the , thus playing a crucial role in the spatial arrangement of the cell.
    ::由三组三微图层组成的九组(九个三胞胎)组成,每个小圆点。九组三胞胎按轮式方向排列。两组垂直放置的中子圆形构成中子体。三胞胎在细胞分裂中非常重要,在细胞分裂中,它们会安排在二次分裂期间分离的线性脊椎。中子位置决定着细胞的位置,从而在细胞的空间结构中发挥着关键作用。

    Centrioles are a very important part of centrosomes, which are involved in organizing microtubules in the cytoplasm . Centrosomes are associated with the nuclear membrane during prophase of the mitosis. In mitosis, the nuclear membrane breaks down and the microtubule organizing center (MTOC) of the centrosome arranges microtubules such that they interact with the chromosomes to build the mitotic spindle.
    ::中子体是中子体中非常重要的一部分,这些中子体参与在细胞托盘中组织微细胞。 中子体在分裂症的预发阶段与核膜有关。 在分裂症中,核膜破裂,而中子体的微囊组织中心(MTOC)安排微细胞组织中心(MTOC),这样它们就能与染色体进行互动,以建立线性脊椎。

    Structure of the centrioles
    Here the centrosome is shown as a pair of orange cylindrical centrioles. They are made of nine triplets of microtubules.

    Junctions
    ::交点

    Junctions are areas between cells that either allow or prevent the movement of materials. Junctions are usually composed of numerous , forming a large molecular complex. Gap junctions, desmosomes and tight junctions are three examples of junctions.
    ::交叉点是允许或阻止材料移动的细胞之间的区域,交叉点通常由众多组成,形成一个大型分子综合体,隔阂交叉点、脱血体和紧凑交叉点是三个交叉点的例子。

    Gap Junctions
    ::差距交叉点

    A gap junction or nexus is a specialized intercellular connection between a variety of cell-types. This junction is a type of "opening," or channel, directly connecting the cytoplasm of two cells, which allows various molecules and ions to pass freely between these cells. One gap junction channel is composed of two connexons which connect across the intercellular space. Six connexins proteins create one connexon (hemichannel) channel. Each connexin protein has four transmembrane . The complete gap junction is a macromolecular complex composed of several to hundreds of individual junctions. Gap junctions are especially important in cardiac muscle cells. The action potential signaling contraction is passed efficiently and effortlessly through gap junctions, allowing the heart muscle cells to contract in tandem. Electrical in the brain also pass through gap junctions. This allows action potentials at the synaptic terminals to be transmitted across to the postsynaptic cell without the need of a neurotransmitter .
    ::空格连接或连接是各种细胞类型之间的一种专门的细胞间连接。 这个连接是两种细胞的“ 打开”或通道,直接连接两个细胞的细胞图层,允许各种分子和离子在这些细胞之间自由传递。 一个空格连接通道由两个连接跨细胞空间的connexons组成。 6个凝聚素蛋白创造了一个锥形( 热气道) 。 每个凝聚素蛋白质有4个交接器。 完整的连接是一个由数至数百个个体连接点组成的大型分子复合体。 隔热点在心脏肌肉细胞中特别重要。 行动信号收缩的可能通过隔热点有效且不费地传递, 使心脏肌肉细胞能够同时连接。 大脑中的电也通过隔热点。 这样可以使突触终端的行动潜力在不需要神经分解器的情况下传递到后的细胞中。

    Gap junctions are analogous to the plasmodesmata that join plant cells.
    ::差距交叉点类似于与植物细胞结合的软体模子。

    Desmosomes
    ::色色素

    A desmosome is a cell junction specialized for cell-to-cell adhesion . They are found in simple and stratified squamous epithelium, and in muscle tissue where they bind muscle cells to one another. These junctions are composed of complexes of cell surface adhesion proteins and linking proteins. These proteins have both an intracellular and extracellular region. Inside the cell, they attach to intracellular filaments of the cytoskeleton . Outside the cell, they attach to other adhesion proteins.
    ::脱血体是专门用于细胞对细胞粘合的细胞交叉点,在简单和分层的粘合性粘合物中和肌肉组织中发现,它们将肌肉细胞相互捆绑在一起。这些交叉点由细胞表面粘合蛋白和连接蛋白组成。这些蛋白质同时具有细胞内和细胞外两个区域。在细胞内,它们附着于细胞骨质的细胞内丝。在细胞外,它们附着其他粘合蛋白。

    The cell adhesion proteins of the desmosome, desmoglein and desmocollin, are members of the cadherin family of adhesion proteins. These proteins are transmembrane proteins that bridge the space between adjacent epithelial cells. The extracellular domains of these cells bind to other cadherin proteins on an adjacent cell. The extracellular domain of the desmosome is called the Extracellular Core Domain (ECD). This is where the two adhesion proteins interact.
    ::脱色、脱moglein和脱mocollin的细胞粘合蛋白是粘合蛋白的卡德黑林家族的成员。 这些蛋白是连接相邻的上皮细胞间空间的转基因蛋白。 这些细胞的外细胞区域与相邻细胞中的其他卡德黑林蛋白结合。 脱色的外细胞区域称为外细胞核心域。 这是两种粘合蛋白相互作用的地方 。

    Tight Junction
    ::紧交点

    Tight junctions are the closely associated areas of two cells. It is a type of junctional complex present only in vertebrates . The corresponding junctions that occur in invertebrates are septate junctions. An example of a tight junction is between epithelial cells in the distal convoluted tubule and the collecting duct part of the nephron in the .
    ::紧接点是两个细胞中紧密相连的区域。它是一种仅存在于脊椎动物中的交接点复合体。在无脊椎动物中出现的相应交接点是静脉交接点。一个紧接点的例子就是分解混凝土管中的上皮细胞与肾脏中采集管段之间的连接点。

    Tight junctions are common at epithelia, which are sheets of cells that form a boundary between a mass of cells and a cavity or space (a lumen ). The membranes of these cells join together, forming a virtually impermeable barrier to fluid. Tight junctions essentially seal adjacent epithelial cells in a narrow layer just beneath their apical surface, which is the portion of the cell exposed to the lumen. The rest of the cell surface is known as the basolateral surface. Tight junctions prevent integral membrane proteins from moving between the apical and basolateral surface, maintaining the properties of those distinct surfaces. For example, receptor-mediated endocytosis occurs at the apical surface and exocytosis at the basolateral surface.
    ::紧凑的连接点在表面很常见,即形成细胞质量与腔或空间(一个润滑物)之间界线的细胞板块。这些细胞的膜结合在一起,形成几乎无法渗透的液体屏障。紧紧的交叉点基本上封存紧邻的皮层,紧紧的一层是紧紧的皮层,该层是接触润滑物的细胞的一部分。细胞表面的其余部分被称为边膜表面。紧紧的交叉点防止整体的膜蛋白在皮层和边表面之间移动,保持这些不同表面的特性。例如,受体中位内分泌疾病发生于显形表面,外在边表面发生。

    Tight junctions are composed of strands of transmembrane proteins embedded in the plasma membranes of two adjacent cells. The extracellular domains of these proteins directly join to one another. These joining proteins associate with peripheral membrane proteins located on the intracellular side of plasma membrane. These peripheral proteins anchor the strands to the actin component of the cytoskeleton, effectively forming a molecular complex that joins together the cytoskeletons of adjacent cells. The major types anchoring proteins of tight junctions are the claudins and the occludins.
    ::紧关口由两个相邻细胞的等离子膜内嵌入的转基因蛋白组成。 这些蛋白的外细胞领域直接相互连接。 这些结合的蛋白质与位于等离子膜内细胞侧端的边缘膜蛋白相关联。 这些外围蛋白把线固定在细胞骨质的活性成分上, 有效地形成分子复合体, 将相邻细胞的细胞骨骼连接在一起。 紧紧关口的主要固存蛋白是单胞和奥克鲁丁。

    In addition to holding cells together, tight junctions play a role in the transport of materials. Tight junctions prevent the passage of molecules and ions through the space between cells. So these molecules and ions must actually enter cells (either by or active transport) in order to proceed through a tissue . This allows tight junctions to indirectly play a role over what substances are allowed into a specific cell. Tight junctions play this role in maintaining the blood-brain barrier.
    ::紧凑的连接点可以防止分子和离子通过细胞之间的空间。因此,这些分子和离子实际上必须进入细胞(通过或主动的传输)才能通过组织。这使得紧紧的连接点可以间接地对特定细胞中允许的物质发挥作用。紧紧的连接点在保持血脑屏障方面起到这一作用。

    Summary
    ::摘要

    • Centrioles are made of short microtubules and are very important in cell division.
      ::Centrioles由短微图层组成,在细胞分裂中非常重要。
    • Cellular junctions allow cell association communication, and adhesion.
      ::细胞交叉点允许细胞联系通信和粘合。

    Review
    ::回顾

    1. What is a cell junction?
      ::什么是囚室交汇处?
    2. Describe the structure of a gap junction. How does the structure relate to its function?
      ::描述一个空隙连接点的结构。 结构与其功能有何关联?
    3. Distinguish between tight junctions and desmosomes.
      ::区分紧要关口和脱血动物

    Explore More
    ::探索更多

    Use this resource to answer the questions that follow.
    ::使用此资源回答下面的问题 。

    1. List the 5 types of intercellular junctions.
      ::列出5种细胞间交叉点。
    2. Briefly describe each type of junction.
      ::1. 简要说明每一类型的连接点。
    3. What is a connexon?
      ::什么是connexon ? (Connexon) ? (Connexon) 是什么? (Connexon? )