Cyanide is rapidly lethal because it blocks
Correct answer: C. cytochrome oxidase, the last carrier of the electron transport chain
- A. glycolysis at the phosphofructokinase step
- B. the ATP synthase channel
- C. cytochrome oxidase, the last carrier of the electron transport chain
- D. the Krebs cycle at citrate synthase
Explanation
Cyanide binds the iron of cytochrome oxidase, so electrons can no longer be passed to oxygen, the whole chain backs up and oxidative phosphorylation stops even though the blood is fully oxygenated. Cells are left with only the two ATP of glycolysis, which the brain and heart cannot survive on. Blocking glycolysis alone would be far less immediately fatal, since aerobic tissues could still use other substrates.
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About Cellular Respiration
Cellular respiration releases energy from glucose through glycolysis, the link reaction, the Krebs cycle and the electron transport chain, producing ATP. The pathway differs in oxygen availability: aerobic respiration uses oxygen and yields more ATP, while anaerobic respiration produces much less ATP and forms lactic acid in muscles or ethanol and carbon dioxide in yeast.
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