Movement down a concentration gradient occurs fairly rapidly over short distances like a micron or so, like the size of a bacterium.

顺浓度梯度扩散在一微米左右的短距离内,相当迅速,一微米相当于一个细菌的大小

耶鲁公开课 - 生物医学工程探索课程节选

In general, inside of a cell molecules move by a process called diffusion.

总的来说,细胞内的分子通过扩散作用来移动

耶鲁公开课 - 生物医学工程探索课程节选