that some of these proteins are transport proteins

有些蛋白质是转运蛋白
and their role in the cell membrane is to allow molecules

他们在细胞膜中所起的作用就是
that the cell needs to come in or to go out.

转运细胞内外所需分子
The glucose transporter is an example of that.

葡萄糖转运蛋白就是个例子
The only way that glucose can get inside cells

葡萄糖进入胞内参与基础代谢的
to provide a substrate for a metabolism is because

唯一途径就是通过
there are specialized proteins in the membrane

细胞膜上的专门蛋白
that allow glucose to cross,

进行跨膜转运
in the same way there are specialized proteins that allow ions to cross.

同样胞膜上还有用于离子转运的专门蛋白
These proteins come in two varieties.

这些蛋白分为两大类
Some are active transport proteins like this one

一类是激活的转运蛋白
which is called the sodium-potassium pump.

比如钠-钾泵