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  • 磷脂

    Diagram illustrating phospholipid structures in a cell membrane.

    Do you feel anything now?
    ::你现在有感觉了吗?

    When you go to the dentist to get a tooth pulled, you really don’t want to feel any pain. The dentist injects an anesthetic into your gum and it eventually becomes numb. One theory as to why anesthetics work deals with the movement of across the cell membrane. The anesthetic gets into the membrane structure and causes shifts in how ions move across the membrane. If ion movement is disrupted, nerve impulses will not be transmitted and you will not sense pain – at least not until the anesthetic wears off.
    ::当你去看牙医去拔牙时,你真的不想感到任何疼痛。牙医将麻醉剂注入你的口香糖,最终会麻木。 关于麻醉剂工作的原因的一个理论是细胞膜之间的移动。 麻醉剂进入膜结构,并导致离子在膜之间的移动。 如果离子运动中断,神经脉冲就不会传播,你也不会感觉到疼痛 — — 至少直到麻醉剂磨损为止。

    Phospholipids
    ::磷脂

    A phospholipid is a that contains a phosphate group and is a major component of cell membranes. A phospholipid consists of a hydrophilic (water-loving) head and hydrophobic (water-fearing) tail (see Figure ). The phospholipid is essentially a in which a fatty has been replaced by a phosphate group of some sort.
    ::磷素是一种含有磷酸盐的成分,是细胞膜的主要成分,磷素由一种(爱水的)顺水的(水的)头和防水的尾巴组成(见图......),磷素基本上是一种脂肪被某种磷酸盐组替代的。

    Diagram illustrating phospholipid structure with hydrophilic head and hydrophobic tails.

    A phospholipid consists of a head and a tail. The “head” of the molecule contains the phosphate group and is hydrophilic, meaning that it will dissolve in water. The “tail” of the molecule is made up of two fatty acids, which are hydrophobic and do not dissolve in water.
    ::磷素由头部和尾部组成,分子的“头”含有磷酸盐组,具有水益性,意味着分子将在水中溶解,分子的“尾”由两种脂肪酸组成,这两种酸是疏水酸,不溶于水中。

    Following the rule of “like dissolves like”, the hydrophilic head of the phospholipid molecule dissolves readily in water. The long fatty acid chains of a phospholipid are nonpolar and thus avoid water because of their insolubility. In water, phospholipids spontaneously form a double layer called a lipid bilayer in which the hydrophobic tails of phospholipid molecules are sandwiched between two layers of hydrophilic heads (see Figure ). In this way, only the heads of the molecules are exposed to the water, while the hydrophobic tails interact only with each other.
    ::按照“类似溶解物”的规则,磷素分子的水利头在水中很容易溶解,磷素长长的脂肪酸链是非极化的,因此由于其溶解性而避免了水;在水中,磷素自发形成一个双层,称为脂质双层,其中磷素分子的疏水尾巴在两层水利分子头之间混合(见图 ) 。 这样,只有分子的头部接触水,而疏水尾巴只相互作用。

    Phospholipid bilayer with hydrophilic heads and hydrophobic tails in water.

    In a water solution, phospholipids form a bilayer where the hydrophobic tails point towards each other on the interior and only the hydrophilic heads are exposed to the water.
    ::在水溶液中,磷素形成两层,疏水尾巴在内部相互指向,只有水利头接触水。

    Phospholipid bilayers are critical components of cell membranes. The lipid bilayer acts as a barrier to the passage of molecules and ions into and out of the cell. However, an important function of the cell membrane is to allow selective passage of certain substances into and out of cells. This is accomplished by the embedding of various molecules in and through the lipid bilayer (see Figure ). These proteins form channels through which certain specific ions and molecules are able to move. Many membrane proteins also contain attached on the outside of the lipid bilayer, allowing it to form with water.
    ::脂质双层是细胞膜的关键组成部分。脂质双层是分子和离子进出细胞的障碍。然而,细胞膜的一个重要功能是允许某些物质有选择地进出细胞。通过将各种分子嵌入和嵌入脂肪双层来实现这一点(见图 )。这些蛋白质形成某些特定的离子和分子能够移动的渠道。许多膜蛋白质还含有与脂肪双层相连的外壳,允许与水形成。

    a phospholipid bilayer showing hydrophobic tails and embedded proteins.

    The phospholipid bilayer of a cell membrane contains embedded protein molecules which allow for selective passage of ions and molecules through the membrane.
    ::细胞膜的磷素双层细胞含有嵌入蛋白分子,可以有选择地将离子和分子通过膜。

     

     

    Science Friday : Candy Corn in Space
    ::科学星期五:太空糖果玉米

    Candy corn is a very tasty treat. In this video by Science Friday , astronaut Don Pettit uses Candy Corn to demonstrate the effects of hydrophobic and hydrophilic interactions.
    ::玉米糖果是一个非常美味的乐谱。在这个由科学星期五拍摄的视频中,宇航员唐·佩蒂特利用玉米糖果展示了疏水和水利相互作用的影响。

     

    Review
    ::回顾

    1. What is a phospholipid?
      ::什么是磷素?
    2. Which part of the phospholipid molecule is water-soluble?
      ::磷素分子的哪个部分可以溶解水?
    3. Which part is not water-soluble?
      ::哪个部分不能溶解水?