Cyanide is a chemical compound that contains monovalent combining group CN. This group consists of a carbon atom triple- bonded to a nitrogen atom. Cyanide is considered to be toxic because it binds to cytochrome c oxidase ie. the fourth complex in the electron transport chain. It attaches to the iron within this protein complex and inhibits the normal activity of the complex system. It binds tightly so that it cannot transport any electrons to oxygen. This blocks the further passage of electrons throughout the chain, halting ATP production. Since no ATP is made, the electron transport chain stops working. This is so because the protons are not allowed to go back into the matrix of the mitochondria, thus, the concentration of protons build up and the gradient becomes large. Therefore, the person is deprived of chemical energy to perform the many numerous processes that sustain life and the person dies.
How cyanide affects the electron transport chain