In some cells they're recycled, that is the cell is able to take up the neurotransmitter after it's released and restore it, but most often there are enzyme systems inside the pre-synaptic membrane where those neurotransmitters are synthesized.

在一些细胞中神经递质可以循环利用,这些细胞可以吸收,已经释放出的神经递质并重新储存起来,但更常见的是突触前膜中含有酶系统,在此合成神经递质

耶鲁公开课 - 生物医学工程探索课程节选

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

耶鲁公开课 - 生物医学工程探索课程节选