Answer: Cyanide is an irreversible enzyme inhibitor of Cytochrome C Oxidase (Complex IV) the fourth complex in the electron transport chain. Cyanide ions bind to the iron atom of the Complex IV in the mitochondrial membrane, which results in blockade of electrons transfer to the final electron acceptor oxygen. This blockade causes build up of proton motive force in the intermembrane space as the protons are not allowed to flow back into the matrix which subsequently halts ATP production. Solution Answer: Cyanide is an irreversible enzyme inhibitor of Cytochrome C Oxidase (Complex IV) the fourth complex in the electron transport chain. Cyanide ions bind to the iron atom of the Complex IV in the mitochondrial membrane, which results in blockade of electrons transfer to the final electron acceptor oxygen. This blockade causes build up of proton motive force in the intermembrane space as the protons are not allowed to flow back into the matrix which subsequently halts ATP production..