Editing Zyklon B (section)

==Mode of action==
{{main|Cyanide poisoning}}
[[Hydrogen cyanide]] is a poisonous gas that interferes with [[cellular respiration]]. [[Cyanide poisoning]] prevents the cell from producing [[adenosine triphosphate]] (ATP) by binding to one of the [[protein]]s involved in the [[electron transport chain]].{{sfn|Nelson|Cox|2000|pp=668, 670–71, 676}} This protein, [[cytochrome c oxidase]], contains [[main subunit of cytochrome c oxidase|several subunits]] and has [[ligand]]s containing iron groups. The cyanide component of Zyklon B can bind at one of these iron groups, [[heme]] a3, forming a more stabilized compound through metal-to-ligand [[pi bond]]ing. As a result of the formation of this new iron–cyanide [[Coordination complex|complex]], the electrons that would situate themselves on the heme a3 group can no longer do so. Instead, these electrons destabilize the compound; thus, the heme group no longer accepts them. Consequently, electron transport is halted, and cells can no longer produce the energy needed to synthesize ATP.{{sfn|Nelson|Cox|2000|pp=668, 670–71, 676}} Death occurs in a human being weighing {{convert|68|kg}} within two minutes of inhaling 70&nbsp;mg of hydrogen cyanide.{{sfn|International Cyanide Management Institute}}{{sfn|Hayes|2004|p=273}}