<unk>  is a potent cytochrome c oxidase (COX, a.k.a Complex IV) inhibitor. As such,<unk>  is a form of histotoxic hypoxia, because it interferes with oxidative phosphorylation. Specifically,<unk>  binds to the heme a3-CuB binuclear center of COX (and thus is a non-competitive inhibitor of it). This prevents electrons passing through COX from being transferred to O2, which not only blocks the mitochondrial electron transport chain but also interferes with the pumping of a proton out of the mitochondrial matrix which would otherwise occur at this stage. Therefore,<unk>  interferes not only with aerobic respiration but also with the ATP synthesis pathway it facilitates, owing to the close relationship between those two processes. One antidote for<unk> , nitrite (i.e. via amyl nitrite), works by converting ferrohemoglobin to ferrihemoglobin, which can then compete with COX for free<unk>  (as the<unk>  will bind to the iron in its heme groups instead). Ferrihemoglobin cannot carry oxygen, but the amount of ferrihemoglobin that can be formed without impairing oxygen transport is much greater than the amount of COX in the body.<unk>  is a broad-spectrum poison because the reaction it inhibits is essential to aerobic metabolism; COX is found in many forms of life. However, susceptibility to<unk>  is far from uniform across affected species; for instance, plants have an alternative electron transfer pathway available that passes electrons directly from ubiquinone to O2, which confers<unk>  resistance by bypassing COX.
Cyanide poisoning
Foreign body aspiration
Chlorine gas poisoning
Carbon monoxide poisoning
Salicylate poisoning
Nitrogen dioxide poisoning
Strychnine poisoning
Tin poisoning