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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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Dialysis, this is an example of a membrane dialysis unit.
透析技术,这里是一个膜透析的装置
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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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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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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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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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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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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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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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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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Well, the way that your immune system recognizes it is that all the cells of our body express a molecule on their surface, a membrane protein called the MHC1 complex.
而免疫系统识别的方法是,身体内所有细胞在其表面表达一种分子,一种叫做MHC1复合体的膜蛋白
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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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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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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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Here is a thin membrane, it's a polymer scaffold, and on that polymer scaffold scientists have placed some skin cells and they've allowed it to grow.
这是一张薄膜,它是一个聚合物支架,在这个支架上,科学家放了一些皮肤细胞,并让它们生长
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That results in a dramatic change in the membrane voltage; the potential across the membrane and that's shown here by this rapid rise in membrane potential.
变化导致了膜电压的剧烈变化,膜电压就是跨膜的电势差,表现为膜电位的迅速上升
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We've talked about one class of molecules, they're transporters that move molecules from inside to outside, or outside to in, that wouldn't ordinarily be transported through a cell membrane.
我们已经讲过一类这样的分子,它们是能够将分子从胞内运至胞外的载体,或者从胞外运至胞内,这个过程不是简单地穿过细胞膜
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Because of that they're barriers, they separate the inside of the cell from the outside of a cell, and only certain kinds of molecules can pass through a cell membrane.
因为它们的屏障作用,将细胞内外区隔开来,只有特定的,某些分子才能穿过细胞膜
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Now, that rapid rise is called depolarization and the membrane is said to be in a depolarized state because it's less polarized or less negatively charged repolarized as negatively charged.
这个迅速上升过程称为去极化,我们称膜处于去极化状态,因为膜的极化程度降低了,或者说是带的负电减少了,而复极化就代表重新带上负电荷
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It has a cell membrane.
细胞都有细胞膜
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They have a nucleus, they have a cell membrane, they have organelles throughout them, they have the same DNA.
它们都有细胞核,细胞膜,细胞器遍布其中,它们有相同的DNA
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