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  • 电化学梯度 - 高级

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    Do you really have electricity flowing through your body?
    ::你真的有电流 通过你的身体?

    Yes, you do. These electrical signals allow information to flow through the extremely rapidly. And it all starts with the formation of an electrochemical gradient.
    ::这些电讯号能让信息通过极快的电流流。 这一切始于电化学梯度的形成。

    The Electrochemical Gradient
    ::电化学梯度

    The of ions across the causes an electrical gradient to build up across this membrane. The number of positively charged ions outside the is usually greater than the number of positively charged ions in the cytosol . This results in a relatively negative charge on the inside of the membrane, and a positive charge on the outside. This difference in charges causes a voltage to exist across the membrane. Voltage is electrical potential energy that is caused by a separation of opposite charges, in this case across the membrane. The voltage across a membrane is the membrane potential . Membrane potential is very important for the conduction of electrical impulses along nerve cells. The membrane potential of a cell at rest is known as its resting potential , and is discussed below. A non-excited nerve cell is an example of a cell at rest.
    ::离子横穿这些离子, 形成一个电梯度, 从而形成横跨此膜的堆积。 在外加正电离子的数量通常大于细胞质中加正电离子的数量。 这导致膜内部的电荷相对负, 外加正电荷。 这种电荷差异导致膜之间的电压存在。 电压是电的潜在能量, 是由相对的电荷分离造成的, 就这里而言, 隔膜的电压。 膜的电压是膜的潜力。 膜的潜力对于神经细胞的电脉冲导非常重要。 休息的细胞的膜潜力被称为它的休息潜力, 下面讨论这个问题。 无热神经细胞是休息的细胞的一个例子。

    Because of the ion gradient, there are less positive ions inside the cell, the inside of the cell is negative compared to outside the cell. This resulting membrane potential favors the movement of positively charged ions (cations) into the cell, and the movement of negative ions (anions) out of the cell. So, there are two forces that drive the of ions across the plasma membrane—a chemical force (the ions' concentration gradient), and an electrical force (the effect of the membrane potential on the ions’ movement). These two forces working together are called an electrochemical gradient .
    ::由于离子梯度,细胞内部的正离子值较低,细胞内与细胞外相比是负的。由此产生的膜潜力有利于将正电离子(cations)移入细胞,以及将负离子(anions)移出细胞。 因此,有两种力量驱动离子穿过等离子膜 — — 一种化学力量(离子浓度梯度 ) , 和一种电力(膜潜力对离子运动的影响 ) 。 这两个力量一起工作,被称为电化学梯度。

    The electrochemical gradient determines the direction an ion moves by diffusion or active transport across a membrane. In and , proton gradients are used to generate a chemiosmotic potential that is also known as a proton motive force , due to both the proton gradient and voltage gradient across the membrane. This potential energy is used for the synthesis of ATP by oxidative phosphorylation .
    ::电化学梯度决定离子通过扩散或活性飘移穿越膜的方向。质子梯度和质子梯度用于产生一种化学反应潜力,由于质子梯度和电压梯度都横跨膜,这种潜在能量被用于氧化磷化合成ATP。

    The Resting Potential
    ::恢复潜力

    In order to maintain the membrane potential, cells maintain a low concentration of sodium ions (Na + ) and high levels of potassium ions (K + ) within the cell (intracellular). The moves three Na + ions out of the cell and brings two K + ions into the cell. This essentially removes one positive charge from the intracellular space. The resulting membrane potential is known as the resting potential.
    ::为了保持膜潜力,细胞在细胞内保持低浓度的钠离子(Na+)和高浓度的钾离子(K+),将3 Na+离子移出细胞,将2 K+离子带入细胞,基本上从细胞内空间去除1个正电荷,由此产生的膜潜力被称为休息潜力。

    Ionic basis of resting membrane potential

    This diagram shows how ions maintain the membrane potential. The sodium-potassium pump is shown in the membrane, transporting three Na + ions (green) out of the cell and bringing two K + ions (blue) into the cell.
    ::本图显示离子如何保持膜潜力。 钠- 钾泵在膜中显示, 将三纳+离子( 绿色) 运出细胞, 并将两K+离子( 蓝色) 带入细胞 。

    The Ion Gradient
    ::爱恩梯度

    The electrochemical potential across a membrane determines the tendency of an ion to cross the membrane. The membrane may be that of a cell or or other sub cellular compartment. The electrochemical potential arises from three factors:
    ::膜上的电化学潜力决定了离子穿过膜的倾向。膜可以是细胞或其他子细胞隔间。电化学潜力来自三个因素:

    1. the difference in the concentration of the ions on either side of the membrane,
      ::离子浓度的差别 在膜两侧的两侧,
    2. the charge of the ions (for example Na + , Ca ++ , Cl - ), and
      ::离子的电荷(例如 Na+、 Ca++、 Cl-) 和
    3. the difference in voltage between the two sides of the membrane (the transmembrane potential).
      ::膜两侧电压差异(变压潜能值)。

    Cotransport of ions by symporters and antiporter carriers is commonly used to actively move ions across biological membranes. Transmembrane ATPases are often involved in maintaining ion gradients. The Na+/K+ ATPase uses ATP to build and maintain a sodium ion gradient and a potassium ion gradient.
    ::交替式ATPase经常参与维持离子梯度,Na+/K+ATPase使用ATP建造和维持离子梯度和钾离子梯度。

    Proton Gradients and ATP synthase
    ::质子梯度和 ATP 合成酶

    One particular ion gradient with biological significance is the proton (H + ) gradient. This type of gradient is established through active transport involving proton pumps. The proton gradient is used during and to generate a chemiosmotic potential, or proton motive force. This potential energy is used for the synthesis of ATP by oxidative phosphorylation. The proton gradient can also be used to store energy for heat production and flagellar rotation.
    ::一种具有生物意义的特定离子梯度是质子(H+)梯度,这种梯度是通过使用质子泵进行主动运输确定的,质子梯度用于使用和产生化学治疗潜力或质子动力,这种潜在能量用于氧化磷化合成ATP,质子梯度也可用于储存热生产能量和旗舰旋转能量。

    The energy held within the proton gradient can be used to synthesize ATP. ATP synthase is a transmembrane that provides energy for the cell to use by producing ATP. The has two distinct regions, F 0 and F 1 . The F 0 is embedded within the membrane, while the F 1 domain is above the membrane, inside the matrix of the mitochondria, or the stroma of the chloroplast. The F 0 region is the proton pore, allowing hydrogen ions to diffuse across the membrane. The F 1 region of the protein has ATP synthesis activity, catalyzing the formation of ATP from ADP and inorganic phosphate. Hence, ATP synthase is both an ion channel protein and enzyme. The synthesis reaction is driven by the proton flow, which forces the rotation of a part of the enzyme; the ATP synthase is a rotary mechanical motor. may also have a version of this enzyme, where it, of course, is embedded in the cell membrane.
    ::质子梯度内持有的能量可用于合成 ATP 。 ATP 合成酶是一种为生产 ATP 时使用的细胞提供能量的转基因体。 它有两个不同的区域, F0 和 F1 。 F0 嵌入膜内, 而 F1 域位于膜之上, 在 mitochondria 的矩阵内, 或 叶质板的粘膜上。 F0 区域是质子孔, 允许氢离子扩散到膜中。 F1 蛋白质的F1 区域有 ATP 合成活动, 从 ADP 和无机磷酸中催化形成 ATP 。 因此, ATP 合成酶既是一个离子通道蛋白质, 也是酶。 合成反应是由质流驱动的, 质流驱动着酶的一部分旋转; ATP 合成酶是一种旋转机械发动机。 此外, 蛋白质素的版本也可能嵌入细胞膜中。

    During within the mitochondria (during cellular respiration) or chloroplast (during photosynthesis) (discussed in the Concept Metabolism (Advanced) concept), a proton gradient is formed when protons are pumped across the membrane by active transport. These hydrogen ions flow back across the membrane by facilitated diffusion through ATP synthase, releasing energy which is then used to convert ADP to ATP (by phosphorylation).  Chemiosmosis is the diffusion of protons across the biological membrane through ATP synthase, due to a proton gradient that forms across the membrane during electron transport.
    ::在mitochondria(在细胞呼吸期间)或氯白(在光合作用期间)(在概念代谢(高级)概念中讨论)期间,质子通过活性运输泵穿过膜,形成质子梯度。这些氢离子通过ATP合成酶加速扩散,释放能量,然后用来将ADP转换为ATP(通过磷酸化),通过ATP合成酶在生物膜中扩散质子,因为电子运输期间在膜中形成质子梯度。

    Summary
    ::摘要

    • The voltage across a membrane is the membrane potential and the membrane potential of a cell at rest is the resting potential.
      ::膜上方的电压是膜潜力,休息时细胞的膜潜力是休息潜力。
    • The electrochemical gradient is composed of a chemical force (the ions' concentration gradient) and an electrical force (the effect of the membrane potential on the ions’ movement).
      ::电化学梯度由化学力(离子浓度梯度)和电力(膜潜力对离子运动的影响)组成。
    • Chemiosmosis is the diffusion of protons across the biological membrane through ATP synthase, due to a proton gradient that forms across the membrane.
      ::Chemiosmosis是质子通过ATP合成酶在生物膜中扩散,因为质子梯度形成于膜中。

    Review
    ::回顾

    1. Define the electrochemical gradient.
      ::定义电化学梯度。
    2. Describe the role of ATP synthase.
      ::描述 ATP 合成酶的作用 。
    3. What is chemiosmosis?
      ::什么是染色体?

    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. Why does an electrochemical gradient form across a cell membrane?
      ::为什么电化学梯度会横跨细胞膜形成?
    2. Why are positive ions attracted to the inside of a cell?
      ::为什么正离子会被细胞内部吸引?
    3. How do ions flow in and out of a cell?
      ::电离子是如何流进和流出细胞的?