this happens spontaneously, you actually get energy out of the reaction as this happens.

这是自发的，当反应发生的时候,你会自发地放出能量。

麻省理工公开课 - 化学原理课程节选

You can become dehydrated and die just as a result of the loss of water there, because of your body's natural response to the infection.

就会脱水,而失水的后果就是死亡,这是你身体对于这种感染的自然反应

耶鲁公开课 - 生物医学工程探索课程节选