These processes occur on the inner mitochondrial membrane.  The ETC consists of four main protein complexes: I, NADH dehydrogenase, II,  succinate dehydrogenase, III, cytochrome complex, and IV, cytochrome oxidase.  In each protein complex, are cofactors, which transfer electrons from NADH and FADH2 to O2.  NADH donates an electron to complex I, releasing NAD+ and an H+ proton.  The electron moves from one cofactor to another, until it reaches O2.  The O2 is then reduced into water.  The electron is able to move along the chain because each consecutive cofactor has a stronger attraction to electrons than the last cofactor.  As the electron passes through complex I, ubiquinone, a cofactor in the chain, and complex IV, protons are pumped from the mitochondrial matrix, into the intermembrane space.  The concentration of H+ builds in the intermembrane space, and the protons are used in chemiosmosis.  The protons are moved through ATP synthase into the mitochondrial matrix, which powers the synthesis of ATP.  ATP is used to provide your body with energy.

When the cyanide ion is present in the body, it binds to the heme prosthetic group, which is a cofactor in cytochrome oxidase.  Cyanide prevents electron flow in the ETC.  This essentially causes a traffic jam within the chain.  Electrons are unable to bind with O2, which prevents other electrons from travelling along the chain.  Since the electrons are unable to pass through the chain, protons do not get pumped into the inner membrane space, and ATP synthase has no protons to synthesize ATP with.  This inability to synthesize ATP starves the body of energy, which will result in your death.

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