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  • 细胞膜

    Lesson
    ::经验教训

     

    A cartoon security guard with sunglasses and a suit, symbolizing cell protection.
     

    Who guards your  cells ?
    ::谁看守你的牢房?

    Not everything can make it into your cells. Your cells have a plasma membrane that helps to guard your cells from unwanted intruders.
    ::并不是每件东西都能进入你的细胞。你的细胞有一个等离子膜来帮助保护细胞不受不受欢迎的入侵者侵袭。

    The Plasma Membrane and Cytosol
    ::Plasma membrane 和 Cytosol 等离子膜

    If the outside environment of a cell is water-based, and the inside of the cell is also mostly water, something has to make sure the cell stays intact in this environment. What would happen if a cell dissolved in water, like sugar does? Obviously, the cell could not survive in such an environment. So something must protect the cell and allow it to survive in its water-based environment. All cells have a barrier around them that separates them from the environment and from other cells. This barrier is called the  plasma membrane , or cell membrane.
    ::如果细胞的外部环境是水基的,而细胞的内部也是水基的,那么,必须保证细胞在这种环境中保持完整。如果细胞在水中溶解,比如糖,会发生什么情况?显然,细胞在这样的环境中是无法生存的。因此,某些东西必须保护细胞,并允许它在其水基环境中生存。所有细胞周围都有一个屏障,将细胞与环境和其他细胞隔离开来。这个屏障被称为血浆膜,或细胞膜。

    The Plasma Membrane
    ::等离子膜

    The plasma membrane ( Figure   ) is made of a double layer of special  lipids , known as  phospholipids . The phospholipid is a lipid  molecule  with a  hydrophilic  ("water-loving") head and two  hydrophobic  ("water-hating") tails. Because of the hydrophilic and hydrophobic nature of the phospholipid, the molecule must be arranged in a specific pattern as only certain parts of the molecule can physically be in contact with water. Remember that there is water outside the cell, and the  cytoplasm  inside the cell is mostly water as well. So the phospholipids are arranged in a double layer (a bilayer) to keep the cell separate from its environment. Lipids do not mix with water (recall that oil is a lipid), so the phospholipid bilayer of the cell membrane acts as a barrier, keeping water out of the cell, and keeping the cytoplasm inside the cell. The cell membrane allows the cell to stay structurally intact in its water-based environment.
    ::等离子膜(Figure)由二层特殊脂质组成,称为磷素,磷素是一种脂质分子,带有一种水益(“爱水”)头部和两条防水尾尾。由于磷素的盐水和疏水性质,分子必须按特定模式排列,因为分子中只有某些部分能与水发生物理接触。要记住,细胞外有水,细胞内的细胞细胞内细胞微粒也大多为水。所以磷素被安排在一个双层(双层)内,以保持细胞与环境的分离。利皮不与水混合(指油是脂质),因此细胞膜的磷素两叶作为屏障,保持细胞内的水,并保持细胞内的细胞微粒。细胞膜允许细胞在水基环境中保持结构完好。

    The function of the plasma membrane is to control what goes in and out of the cell. Some molecules can go through the cell membrane to enter and leave the cell, but some cannot. The cell is therefore not completely permeable. "Permeable" means that anything can cross a barrier. An open door is completely permeable to anything that wants to enter or exit through the door. The plasma membrane is  semipermeable , meaning that some things can enter the cell, and some things cannot.
    ::等离子膜的功能是控制细胞的进出。 有些分子可以通过细胞膜进入和离开细胞, 但有些分子不能。 因此, 细胞不能完全渗透。 “ 可渗透性” 意味着任何东西都可以跨过屏障。 一个打开的门可以完全渗透到任何想要进入或走出门的任何东西。 等离子膜是半渗透的, 意味着有些东西可以进入细胞, 有些东西不能进入。

    The plasma membrane structure showing phospholipid bilayer and proteins.
     
    Plasma membranes are primarily made up of phospholipids (red/yellow). The hydrophilic ("water-loving") head and two hydrophobic ("water-hating") tails are shown. The phospholipids form a bilayer (two layers). The middle of the bilayer is an area without water. There can be water on either side of the bilayer. There are many proteins (blue) scattered throughout the membrane.

    Cytosol
    ::共聚溶

    The inside of all cells also contains a jelly-like substance called  cytosol . Cytosol is composed of water and other molecules, including  enzymes , which are  proteins  that speed up the cell’s  chemical reactions . Everything in the cell sits in the cytosol, like  fruit  in a jello dessert. The term cytoplasm refers to the cytosol and all of the  , the specialized compartments of the cell. The cytoplasm does not include the  . As a  prokaryotic cell  does not have a nucleus, the   is in the cytoplasm.
    ::所有细胞的内部也含有一种类似果冻的物质,叫做细胞质素。细胞质素由水和其他分子组成,包括酶,这些分子是加速细胞化学反应的蛋白质。细胞内的所有物质都位于细胞质素中,就像切罗甜点中的水果一样。细胞质素一词指细胞质素和细胞的所有专门隔间。细胞质素不包括细胞。由于一个蛋白质细胞没有核,所以细胞质素就存在于细胞质素中。

    Summary
    ::摘要

    • The plasma membrane is formed by a phospholipid bilayer.
      ::等离子膜由一个磷素双层造成。
    • The plasma membrane controls what moves inside and outside the cell.
      ::等离子膜控制细胞内外的移动。
    • The cytosol is the jelly-like material in which the contents of the cell are suspended.
      ::细胞索是软体状物质 细胞内装物被悬浮的果冻状物质

    Explore More
    ::探索更多

    Use the resource below to answer the following questions.
    ::使用以下资源回答下列问题。

    • The Plasma Membrane  at   (5:16)
      ::5:16时的等离子膜(5:16)

     

     

    1. What makes up the "head" region of a phospholipid? Is it hydrophobic or hydrophilic?
      ::何为磷素的“头”区域?
    1. What makes up the "tail" region of a phospholipid? Is it hydrophobic or hydrophilic?
      ::是什么构成磷素的“尾部”区域?是疏水症还是嗜水症?
    1. What happens when you drop a phospholipid in water?
      ::当你把磷素丢进水里时会怎样?
    1. How are phospholipids arranged in a plasma membrane?
      ::磷素如何安排在等离子膜中?
    1. What is a glycoprotein? What is one of the uses of glycoproteins?
      ::甘醇蛋白是什么? 甘醇蛋白有什么用?
    1. What is "Brownian movement"? How is this movement related to the cell membrane?
      ::"布朗运动"是什么?

    Review
    ::回顾

    1. What is the plasma membrane?
      ::等离子膜是什么?
    1. Describe a phospholipid.
      ::描述磷素。
    1. What are the components of the cytosol?
      ::细胞索的成分是什么?
    1. What is meant by the description of the plasma membrane as “semipermeable”?
      ::将等离子膜描述为“可扩散”是什么意思?
    1. What is the difference between the cytosol and the cytoplasm?
      ::细胞溶液和细胞顶板板之间有什么区别?