President Obama had this reaction to Thursday's report on the gross domestic product a wide measure of goods and services in the economy.

VOA: special.2009.10.30

A reaction performed by one enzyme creates a product that stimulates another enzyme that creates a product, and stimulates another enzyme, and through this cascade of reactions you amplify and carry the signal forward.

一种酶催化生成的产物会活化另一种酶,而它催化的产物又能激活其他酶,催化反应生成另一种产物,通过这层层反应,信号被放大,并不断向前传递

耶鲁公开课 - 生物医学工程探索课程节选