章节大纲

  • 常规

    全部折叠 展开全部

  • 膜蛋白

    What will you learn
    ::你会学到什么

    • Types of membrane proteins
      ::膜蛋白质类型
    • The of the
      ::会 议 日 排 排 排 排 排 排 日 排 排
    • Different types of extensions of the cell membrane and their role in movement
      ::细胞膜扩展及其在移动中的作用的不同类型

    Cross-section of a cell highlighting the semipermeable membrane and membrane proteins.

    Can anything or everything move in or out of the cell?
    ::任何东西或一切 移动在或走出牢房?

    No. It is the semipermeable cell membrane that determines what can enter and leave the cell. So, if not everything can cross the membrane, how do certain things get across?
    ::不,是半渗透细胞膜决定了什么可以进入和离开细胞。所以,如果不是每件事都能穿过细胞膜,那么某些事情怎么经过呢?

    Membrane Proteins
    ::膜蛋白

    The cell membrane contains molecules other than phospholipids, primarily other and . The yellow molecules between the phospholipid tails in the Figure  , for example, are the lipid cholesterol. Molecules of cholesterol help the cell membrane keep its shape. Many of the proteins in the cell membrane assist other substances in crossing the membrane.
    ::细胞膜含有除磷素以外的分子,主要是其他分子和分子。图中磷素尾巴之间的黄色分子是脂质胆固醇。胆固醇的分子会帮助细胞膜保持其形状。细胞膜中的许多蛋白质会帮助其他物质穿越膜。

    The cell membranes also contain certain types of proteins. A membrane protein is a protein molecule that is attached to, or associated with, the membrane of a cell or an . Membrane proteins can be put into two groups based on how the protein is associated with the membrane.
    ::细胞膜还含有某些种类的蛋白质。膜蛋白是一种蛋白质分子,附于或与细胞或细胞的膜有关。根据蛋白质如何与膜有关,可以将膜蛋白分成两组。

    Integral membrane proteins are permanently embedded within the cell membrane. They have a range of important functions. Such functions include channeling or transporting molecules across the membrane. Other integral proteins act as cell receptors. Integral membrane proteins can be classified according to their relationship with the bilayer:
    ::内分泌膜蛋白永久嵌入细胞膜内,具有一系列重要功能。这些功能包括通过膜穿透输送或输送分子。其他内分蛋白作为细胞受体。内分泌膜蛋白可以根据它们与双层的关系进行分类:

    • Transmembrane proteins span the entire cell membrane. Transmembrane proteins are found in all types of biological membranes.
      ::跨膜蛋白横跨整个细胞膜,在所有类型的生物膜中都发现了跨膜蛋白。
    • Integral monotopic proteins are permanently attached to the membrane from only one side.
      ::单项内分泌蛋白单体蛋白只从一面永久附在膜上。

    Some integral membrane proteins are responsible for cell adhesion (sticking of a cell to another cell or surface). On the outside of cell membranes and attached to some of the proteins are chains that act as labels that identify the cell type. Shown in the Figure  are two different types of membrane proteins and associated molecules.
    ::细胞粘合(将细胞粘合到另一个细胞或表面)由一些内分泌膜蛋白组成。在细胞膜外和附于某些蛋白质的链条作为标明细胞类型的标签。图中显示的是两种不同的膜蛋白和相关分子。

    DID YOU KNOW?
    Glycoproteins and glycolipids have a carbohydrate chain that acts as a label to identify the cell type. Specifically, A, B, O groups result from having different carbohydrate chains on the cell surface of red blood cells .
     

    Peripheral membrane proteins are proteins that are only temporarily associated with the membrane. They can be easily removed, which allows them to be involved in cell signaling. Peripheral proteins can also be attached to integral membrane proteins, or they can stick into a small portion of the lipid bilayer by themselves. Peripheral membrane proteins are often associated with ion channels and transmembrane receptors. Most peripheral membrane proteins are hydrophilic .
    ::外膜蛋白是蛋白质,仅与膜暂时相关,可以很容易地去除,从而可以让他们参与细胞信号工作。外膜蛋白也可以附在内膜蛋白中,也可以自己粘在少量的脂质双层中。外膜蛋白往往与离子通道和转膜受体相关。大多数周边的膜蛋白都具有水利功能。

    Membrane proteins and their structures in a cellular membrane context.
    Some of the membrane proteins make up a major transport system that moves molecules and ions through the polar phospholipid bilayer.
    DID YOU KNOW?

    Phospholipase is an that breaks down various bonds in the polar head group of phospholipids. These enzymes are important to help break down damaged or aged cell membranes. This enzyme represents an example of a peripheral membrane protein.
    ::磷磷脂酶在磷素的极头组中打破了各种联结。 这些酶对于帮助破碎受损或衰老的细胞膜非常重要。 这种酶代表了边缘膜蛋白的一个例子。

     

    The Fluid Mosaic Model
    ::流流摩西模型

    In 1972, S.J. Singer and G.L. Nicolson proposed the now widely accepted Fluid Mosaic Model of the structure of cell membranes. The model proposes that integral membrane proteins are embedded in the , as seen in the Figure  . Some of these proteins extend all the way through the bilayer, and some only partially across it. These membrane proteins act as transport proteins and receptors proteins.
    ::1972年,S.J.Singer和G.L.Nicolson提出了目前广泛接受的细胞膜结构流体摩西模型。该模型建议,如图所示,内含的膜蛋白质应嵌入细胞膜结构中。其中一些蛋白质贯穿两层,有些仅部分贯穿于两层。这些膜蛋白质作为运输的蛋白质和受体蛋白质。

    Their model also proposed that the membrane behaves like a fluid, rather than a solid. The proteins and lipids of the membrane move around the membrane, much like buoys in . Such movement causes a constant change in the "mosaic pattern" of the cell membrane.
    ::他们的模型还提出膜行为要像液体,而不是固态的。 膜的蛋白质和脂质在膜周围移动,就像浮标一样。这种移动导致细胞膜的“海洋模式”不断发生变化。

     

     

    Extensions of the Cell Membrane
    ::细胞膜膜的扩展

    The cell membrane may have extensions, such as whip-like flagella or brush-like cilia . In single-celled organisms , like those shown in the Figure , the membrane extensions may help the organisms move. In , the extensions have other functions. For example, the cilia on human lung cells sweep foreign particles and mucus toward the mouth and nose.
    ::在单细胞生物中,如图中所示的,膜扩展可以帮助生物移动。在“细胞膜”中,扩展具有其他功能。例如,人体肺细胞的硅膜将外来颗粒和粘膜扫向口鼻。

    • Microscopic view of single-celled organisms with membrane extensions, such as flagella and cilia.
      Microscopic view of cellular extensions, showing structures resembling cilia and flagella.
    Flagella in Chlamydomonas and Cilia in Bronchiolar epithelium. Flagella and Cilia are extensions of the cell membrane of many cells.

    Summary
    ::摘要

    • The cell membrane has many proteins that assist other substances in crossing the membrane.
      ::细胞膜含有许多蛋白质,帮助其他物质跨越膜。
    • The Fluid Mosaic Model depicts the biological nature of the cell membrane.
      ::流体摩西模型描述细胞膜的生物性质。
    • Cilia and flagella are extensions of the cell membrane.
      ::Cilia和Flagella是细胞膜的延伸。

    Review
    ::回顾

    1. What is the main difference between the two main types of proteins associated with the cell membrane?
      ::与细胞膜相关的两种主要蛋白质的主要区别是什么?
    2. What are two functions of integral membrane proteins?
      ::复合膜蛋白的两种功能是什么?
    3. Discuss the Fluid Mosaic Model.
      ::讨论流体摩西模型。
    4. What are flagella and cilia?
      ::什么是白旗和西利亚?