Why does cyanide is so fast acting?

Cyanide is a fast-acting poison because it binds rapidly to cytochrome c oxidase, an essential enzyme in the mitochondrial electron transport chain. This binding inhibits cellular respiration by preventing cells from using oxygen, leading to cellular asphyxiation. The swift disruption of aerobic metabolism causes rapid onset of symptoms and can lead to death within minutes if not treated promptly. Additionally, cyanide's small molecular size allows it to quickly penetrate biological membranes and tissues.