Why is cyanide (KCN) toxic to cells?

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Multiple Choice

Why is cyanide (KCN) toxic to cells?

Cyanide blocks the mitochondrial electron transport chain, stopping oxidative phosphorylation. It binds to cytochrome c oxidase (complex IV) and prevents electrons from being passed to oxygen, so proton pumping across the inner membrane ceases. Without a proton gradient, ATP synthase can’t make ATP, causing a rapid drop in cellular ATP. Cells then rely on anaerobic glycolysis for a quick energy burst, which is inefficient and leads to lactic acidosis and metabolic stress. This energy failure is why cyanide is so toxic. The other options don’t fit because cyanide doesn’t directly inhibit glycolysis, doesn’t target ATP synthase itself, and doesn’t cause uncontrolled ATP production.

Cyanide blocks the mitochondrial electron transport chain, stopping oxidative phosphorylation. It binds to cytochrome c oxidase (complex IV) and prevents electrons from being passed to oxygen, so proton pumping across the inner membrane ceases. Without a proton gradient, ATP synthase can’t make ATP, causing a rapid drop in cellular ATP. Cells then rely on anaerobic glycolysis for a quick energy burst, which is inefficient and leads to lactic acidosis and metabolic stress. This energy failure is why cyanide is so toxic. The other options don’t fit because cyanide doesn’t directly inhibit glycolysis, doesn’t target ATP synthase itself, and doesn’t cause uncontrolled ATP production.

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