4.26 扩散 -- -- 先进
章节大纲
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What will eventually happen to these dyes?
::这些染料最终会怎样?They will all blend together. The dyes will move through the until an even distribution, or equilibrium, is achieved. The process of moving from areas of high amounts of a substance to areas of low amounts of the same substance is called diffusion.
::它们都会混合在一起。染料将一直移动到均衡分布或平衡实现。从一种物质的高含量地区迁移到同一物质的低含量地区的过程被称为扩散。Diffusion
::传播is a way that small molecules or ions move across the without input of energy by the . The three main kinds of passive transport are diffusion (or simple diffusion), , and facilitated diffusion . Simple diffusion and osmosis do not involve transport proteins . Facilitated diffusion requires the assistance of .
::微小分子或离子在没有能量投入的情况下移动。三种主要的被动迁移方式是扩散(或简单的扩散),以及便利扩散。简单的扩散和渗透不涉及迁移蛋白。促进扩散需要...的帮助。Diffusion is the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration. For , diffusion is the movement of small molecules across the cell membrane. The difference in the concentrations of the molecules in the two areas is called the concentration gradient . The kinetic energy of the molecules results in random motion, causing diffusion. In simple diffusion, this process proceeds without the aid of a transport protein. it is the random motion of the molecules that causes them to move from an area of high concentration to an area with a lower concentration.
::扩散是分子从分子高度集中的区域向低浓度区域的移动。 因为扩散是小分子跨细胞膜的移动。 这两个区域分子浓度的差异被称为浓度梯度。 分子的动能导致随机运动, 导致扩散。 在简单扩散中, 这个过程在没有迁移蛋白的帮助下进行。 分子的随机运动导致它们从高浓度区域转移到低浓度区域。Diffusion will continue until the concentration gradient has been eliminated. Since diffusion moves materials from an area of higher concentration to the lower, it is described as moving solutes "down the concentration gradient." The end result of diffusion is an equal concentration, or equilibrium , of molecules on both sides of the membrane. At equilibrium, movement of molecules does not stop. At equilibrium, there is equal movement of materials in both directions.
::扩散将持续到浓度梯度被消除为止。 由于扩散将材料从高浓度地区移到低浓度地区, 它被描述为将溶液“ 向浓度梯度下移 ” 。 扩散的最终结果是分子在膜两侧的浓度或平衡。 平衡时, 分子的移动不会停止。 在平衡时, 物质在两个方向上都有相同的移动 。If a molecule can pass freely through a cell membrane, it will cross the membrane by diffusion ( Figure ). The inside of the plasma membrane is hydrophobic , so certain molecules cannot easily pass through the membrane. Recall the semipermeable nature of the bilayer. Molecules that cannot easily pass through the bilayer include ions and small hydrophilic molecules, such as glucose , and macromolecules, including proteins and . Examples of molecules that can easily diffuse across the plasma membrane include carbon dioxide and oxygen gas. These molecules diffuse freely in and out of the cell, along their concentration gradient. Though water is a polar molecule, it can also diffuse through the plasma membrane. The diffusion of water through the cell membrane is of such importance to the cell that it is given a special name, osmosis .
::如果分子可以通过细胞膜自由穿透细胞膜,它将通过扩散穿过膜(Figure)。等离子膜的内部是疏水性,因此某些分子无法轻易通过膜。回顾两层的半渗透性质。不能轻易通过两层的分子包括离子体和小水利分子,如葡萄糖,以及包括蛋白在内的大型分子。可以很容易地跨过等离子膜扩散的分子的例子包括二氧化碳和氧气。这些分子在细胞内部和之外自由扩散,沿着其浓度梯度自由扩散。虽然水是一种极分子,但它也可以通过等离子膜扩散。通过细胞膜扩散水对细胞具有如此重要的意义,因此给细胞取了一个特殊的名称,即宇宙。Molecules move from an area of high concentration to an area of lower concentration until an equilibrium is met. The molecules continue to cross the membrane at equilibrium, but at equal rates in both directions.
::分子从高浓度地区移到低浓度地区,直到达到平衡。分子在平衡时继续穿过膜,但双向的速率相等。Summary
::摘要-
The cell membrane is selectively permeable, allowing only certain substances to pass through.
::细胞膜有选择性地渗透,只允许某些物质通过。 -
Passive transport is a way that small molecules or ions move across the cell membrane without input of energy by the cell. The three main kinds of passive transport are diffusion, osmosis, and facilitated diffusion.
::被动迁移是一种小分子或离子在没有细胞能量输入的情况下穿过细胞膜的方式,主要的三种被动迁移方式是扩散、渗透和便利扩散。 -
Diffusion is the movement of molecules from an area of high concentration of the molecules to an area with a lower concentration.
::扩散是指分子从分子高度集中的区域向低浓度区域的移动。
Review
::回顾-
What is diffusion? What is the main difference between simple diffusion and facilitated diffusion?
::什么是传播?简单传播与便利传播之间的主要区别是什么? -
What is a concentration gradient?
::什么是浓度梯度? -
What happens at equilibrium?
::平衡时会发生什么?
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The cell membrane is selectively permeable, allowing only certain substances to pass through.
