Cyanide blocks the transfer of electrons from cytochrome c oxidase (Complex IV) to oxygen in the mitochondrial electron transport chain. What is the most immediate consequence of cyanide poisoning on cellular respiration?

Core Concept

Complex IV passes electrons to oxygen, the final electron acceptor. When cyanide blocks this complex, the entire electron transport chain backs up and stops. Without electron flow, protons are not pumped, the electrochemical gradient collapses, and ATP synthase cannot generate ATP via chemiosmosis.