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

耶鲁公开课 - 生物医学工程探索课程节选

They're not responsible necessarily for moving molecules inside and out, but they sit at the outside of the cell and they wait for signals.

它们不负责将分子运进运出,而是冲着细胞外面坐等信号

耶鲁公开课 - 生物医学工程探索课程节选