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They go across the membrane - this is the trans-membrane part of the receptor that's going across the membrane.
它们跨越式的存在于细胞膜上,这就是受体的跨膜部分,它跨越了细胞膜
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These proteins have functions that are essential for life of the cell, they transport molecules back and forth across the membrane.
这些蛋白所起的功能,对于细胞生存至关重要,它们负责转运分子通过细胞膜进出细胞
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Essentially, what they are is it's a protein that spans the membrane of a cell.
本质上来说，它是一个横跨细胞膜的蛋白质。
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It has to be small, and it has to be lipid soluble in order for it to pass through a cell membrane.
这些分子必须非常小,而且必须是脂溶性的,才能穿过细胞膜
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Now, this is in the resting state of all cells, there's some membrane potential and neurons have this resting membrane potential also.
现在这是一个静息状态的细胞,它具有膜电位,神经元也具有类似的静息电位
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It does so because there are some molecules in the surface of the membrane that allow glucose to move in and out.
而这个过程的完成依赖于,膜表面存在的一些分子,这些分子能够将葡萄糖运进或者运出细胞
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I mentioned a little bit that this membrane is not just lipid bilayer but there's also proteins that are inserted into the membrane.
我之前说过,这层膜不仅仅是一层脂质双分子层,而是有很多蛋白质嵌插在膜上的
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That general class of molecules is called receptors and its shown here just as a block of material living in the cell membrane.
这一类分子叫做受体,在这里看起来就像是,生活在细胞膜内的物质
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I've already mentioned many times that the lipid bilayer, the cell membrane, isn't just a lipid bilayer.
我已经讲过很多遍这个脂质双分子层了,细胞膜它不只是一个脂质双分子层
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That potential difference is generated by the movement of ions, principally sodium and potassium across the membrane.
电势差是由离子运动造成的,特别是钠和钾的跨膜运动
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Now, what happens during an action potential is that that membrane potential changes very rapidly and it changes from being negative to being more positive.
在动作电位产生时,膜电位迅速改变,从较负的电位向更正的电位改变
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We talked about the cell membrane, the plasma membrane separating the inside form the outside.
我们讲过细胞膜,这种质膜将细胞内外区分开
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So they like to be in the membrane and they're stable there and they won't come out because their structure allows them to exist in these unique spaces.
所以它们在膜里稳定存在,而且也不会脱离膜,因为这些蛋白质的结构使其能存在于,磷脂双分子层这个独特的环境中
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This process, which is shown schematically here, as a vesicle fusing with the cell membrane and then dropping its neurotransmitter only happens when an action potential reaches the end of the axon.
这一过程 扼要地展示在这里,小泡同细胞膜融合,释放其神经递质,这只发生在动作电位抵达轴突末梢时
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For now, just picture it in this simple way as a molecule, usually a protein, that's embedded in the cell membrane and many receptors have a part of them that is extracellular.
现在,我只把这种分子图示出来,受体通常是一种蛋白质,它们镶嵌在细胞膜上,很多受体还有部分结构露在细胞外
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There's a local change in the membrane, that local change involves opening of channels that allow ions to pass through regions where they couldn't pass through before, that results in a change in voltage.
膜上会发生局部变化,局部变化包括离子通道开启,使离子通过,先前不能通过的区域,从而引起电压的变化
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It refers to usually 'receptors' that are fixed in a cell, on a cell membrane, and 'ligands' which are dispersed throughout the body and free to diffuse around, and occasionally will find the cell.
受体这个词通常代表了,固定于细胞表面的分子,而配体分散于体内各处,能够自由扩散,它们偶尔会与细胞邂逅
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That happens, and if I was looking at a region of membrane that was experiencing an action potential I would see voltage change in just the way it's shown in this graph here.
当去极化发生时,如果我观察一个经历动作电位的区域,我就会看到这样的电压变化,就像这幅图上展示的一样
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Now, sodium and potassium don't ordinarily move across membranes, they're charged molecules, they can't dissolve, they can't permeate through a cell membrane, but they go through because there are channels that allow them to pass through in the membrane.
钠和钾通常是不能跨过细胞膜的,它们都是带电粒子,它们不能溶解在细胞膜中,不能渗透通过细胞膜,但它们之所以能通过细胞膜,全赖膜上离子通道的作用
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In some cells they're recycled, that is the cell is able to take up the neurotransmitter after it's released and restore it, but most often there are enzyme systems inside the pre-synaptic membrane where those neurotransmitters are synthesized.
在一些细胞中神经递质可以循环利用,这些细胞可以吸收,已经释放出的神经递质并重新储存起来,但更常见的是突触前膜中含有酶系统,在此合成神经递质
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It would generate an electrical signal because it would - you'd open the ion channel and you would ion fluxes and you would change the membrane potential in just the way I described for the action potential.
它会产生一个电信号,因为--,离子通道会打开,产生离子流,膜电位会改变,像我讲动作电位时那样
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This is a picture of patch clamp, it's a device that engineers built to fasten onto individual cells in order to look at how molecules in the membrane of the cell are working, and I'll talk a little bit about that as we go along.
这是膜片钳的图片,工程师使用该装置固定单个细胞,由此观察,细胞膜中的分子怎样活动,在以后的课中我还会谈到这方面内容
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On the side over here shows a cell membrane and so this is outside the cell above it, and this is inside the cell below, and this is the lipid bilayer that separates the outside of the cell from the inside of the cell.
这边这个表示细胞膜,它的上面代表细胞外部,下面代表细胞内部,这个是脂质双分子层,将细胞内外分开
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Insulin, the ligand binds to its receptor, creates a change through a kinase activity that's exposed, which leads to other biochemical changes, which leads to a change in cell behavior - in this case the cell behavior is that more glucose transporters are brought to the membrane and more glucose can enter the cell.
胰岛素,一种能够与受体结合的配体,通过其暴露出的激酶活性引起的变化,导致了其它后续生化变化的发生,进而使细胞行为发生改变,这个例子中的细胞行为就是,更多的糖载体被带到细胞膜表面,这样更多的糖分子进入到细胞内部
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They carry a potential, that is, if you could - if you had a tiny, tiny electrical meter, you could one put one electrode on one side of the cell membrane, on the extracellular side and one on the intracellular side and measure, you would measure a potential difference; just like a battery you would measure a potential difference.
它们带有电势,就是说,如果你能有一个足够小的电位计,可以把一个电极放在细胞膜一侧,假设放在细胞外的一侧,另一个电极放在细胞内侧并测量,你能测到一个电势差,就像电池那样能测到电势差
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So, for example, if we look at sodium channels, and sodium channels are some of the particularly prevalent ones when we're talking about neurons, if you think about the cell membrane, and this little green cartoon is me trying to show a sodium channel here, and in this case, you can see that it's closed, such that no ions are getting through.
比如，让我们来看一下钠离子通道，钠离子通道是我们会经常遇到的几个之一,在讨论神经元的时候，如果大家想想细胞膜，而这个绿色的小示意图就是我用来表示,钠离子通道的，在这种情况下，大家可以看到它是关闭的，因此没有离子可以通过。
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If a cell membrane was indeed just a lipid bilayer, then glucose could never enter the cell because it can't permeate through cell membranes.
如果细胞膜只是一个脂质双分子层的话,葡萄糖就不可能进入细胞,因为它不能渗透过细胞膜
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That change happens because something gets triggered in the membrane, and what gets triggered is a voltage gated sodium channel, which is shown here.
变化的原因是膜上某些东西被触发了,被触发的是钠离子电压门控通道,展示在这儿了
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So, this is called the extracellular region or domain, this is the trans-membrane region or domain, and this is the cytoplasmic region or domain.
因此,这部分叫做胞外区,中间这部分叫做跨膜区,内部这一段叫做胞质区
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It's encased within a membrane, a cell membrane which we talked about the structure of.
都是膜包围细胞器,我们刚讲过其结构的那种膜
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