Cyanide toxicity best described by which mechanism?

Cyanide toxicity best described by which mechanism?

• A. It inhibits oxidative phosphorylation.
• B. It stimulates ATP production.
• C. It inhibits the electron transport chain at complex II.
• D. It interferes with DNA replication.

Answer: (A)

The mechanism tested is how cyanide disrupts cellular energy production. Cyanide binds to the ferric iron in cytochrome c oxidase, the enzyme of Complex IV in the mitochondrial electron transport chain. This blocks the transfer of electrons to oxygen, halting the proton pumping that drives ATP synthesis by oxidative phosphorylation. With oxidative phosphorylation shut down, cells can’t efficiently make ATP despite normal oxygen levels, so they switch to anaerobic glycolysis, which leads to lactic acidosis. This is why cyanide toxicity is best described as inhibition of oxidative phosphorylation. It does not stimulate ATP production, and it does not act at Complex II or interfere with DNA replication.

The mechanism tested is how cyanide disrupts cellular energy production. Cyanide binds to the ferric iron in cytochrome c oxidase, the enzyme of Complex IV in the mitochondrial electron transport chain. This blocks the transfer of electrons to oxygen, halting the proton pumping that drives ATP synthesis by oxidative phosphorylation. With oxidative phosphorylation shut down, cells can’t efficiently make ATP despite normal oxygen levels, so they switch to anaerobic glycolysis, which leads to lactic acidosis. This is why cyanide toxicity is best described as inhibition of oxidative phosphorylation. It does not stimulate ATP production, and it does not act at Complex II or interfere with DNA replication.