Similar chemicals can have vastly different biological characteristics, like if one can bind to a certain nueroteceptor (or pass the blood-brain barrier in the

Similar chemicals can have vastly different biological characteristics, like if one can bind to a certain nueroteceptor (or pass the blood-brain barrier in the first place) or not. Chloride is a basic chemical used by the body. Take away an ion and make it chlorine, and it is fatal in very small quantities.