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These are molecules that exist naturally in cell membranes and are activated by certain enzymes and kinases generated by receptors.
这些分子存在于细胞膜表面,能被受体激活的某种酶或激酶所活化
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It can't enter cells because it's too big and it's too water soluble so it can't go through cell membranes.
它的分子太大了所以无法进入细胞,而且还是水溶性的,所以它也无法穿过细胞膜
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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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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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I mentioned earlier, we thought about receptors as being these blocks and membranes but there are different families of receptors.
我之前讲过,我们把受体看做一类,固定在细胞膜上的分子,但受体有许多不同家族
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Many of them are derived from cholesterol and they're hydrophobic, which means they can penetrate through cell membranes.
多数分子都来自于胆固醇,它们是疏水性的,这意味着它们能够穿过细胞膜
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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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There's lipid chains in between so cell membranes are lipid rich layers that can exist in water.
脂质链在两者中间,所以细胞膜是富含脂类的膜层,并可以稳定存在于水中
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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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All cell membranes have these channels within them, and under their resting conditions sodium is moving from outside to inside, potassium's moving from inside to outside.
所有细胞膜上都有这种通道结构,在静息状态下,钠从细胞外流向细胞内,钾从细胞内流向细胞外
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It's less negatively charged than it is in its resting state.
细胞膜此时比静息状态带负电减少
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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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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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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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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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So most of the lipids, which make up cell membranes in your body are of this category of phospholipids.
大部分脂类,那些在你体内构成细胞膜的脂类,都属于磷脂类
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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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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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There are - that's one class of proteins on the surface I'm sorry.
对不起,这是细胞膜蛋白的一个种类
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It turns out that one of the places that's been very fruitful to look for proteins that differ between cell populations is on the surface of the cell.
而事实证明,寻找能鉴别细胞种类的,特定蛋白的最佳位置,是在富含蛋白的细胞膜上
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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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I wanted to introduce it to you so that if you don't haven't heard about this before you might want to read a little bit about this before we get to Chapter 5.
我想给你们介绍一下细胞膜,所以如果你没有,以前没听说过这个的话,也许你在学到第五章之前,要读一点关于这些的文献
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It has a cell membrane.
细胞都有细胞膜
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Because these molecules can span across the membrane from outside to inside, they're in just the right position to take messages that they receive from outside the cell and transmit them through the membrane into the cells internal apparatus, and that's what they do.
因为这些分子能穿过细胞膜,连通细胞内外,它们所在的位置非常适于接受信息,它们能将外界获得的信息,通过细胞膜传递给细胞器,这正是它们的功能
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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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