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
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
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。
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
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
There's another whole family of molecules that sit in the surface.
在细胞膜上还存在着另一类分子
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
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
That RNA is made into proteins, and proteins are the working molecules of the cell, they're enzymes, they're structural molecules, they're are proteins that exist in the membrane that allow things to go in and out of the cell, so really the working molecules are the cell in every sense.
这些RNA指导合成蛋白质,蛋白质是细胞生命活动的承担者,它们可以是酶,或是结构性分子,也可以存在于细胞膜上的膜蛋白,能够让一些物质通过它们进出于细胞,所以蛋白质才是真正意义上,细胞生命活动的承担者
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