Probably nature doesn't care about the way we classify the mechanisms. There are lock-and-key mechanisms (receptors), weak interactions, combinatorial interacti

Probably nature doesn't care about the way we classify the mechanisms. There are lock-and-key mechanisms (receptors), weak interactions, combinatorial interactions, signals (neural signals), boolean networks (gene switching) etc. As an electrical engineer, who did Ph.D. in system biology, I wa s fascinated by the different routes biology takes to do seemingly same computation. As someone said, "Nothing in Biology Makes Sense Except in the Light of Evolution". If there is a way to select a mechanism that gives a real advantage to the organism, then it doesn't matter which bucket it falls into. PS: I was also amused by the lack of sinusoids and an abundance of sigmoids in biochemistry.