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JEE Main levelSingle correct optionDifficulty 2 of 3ev024

Carbon monoxide is highly toxic because it

  1. Areacts with the globin chain and breaks the peptide bonds
  2. Boxidises Fe(II) of haem to Fe(III), giving methaemoglobin
  3. Cdissolves in plasma and lowers the blood pH sharply
  4. Dbinds to the Fe(II) of haem more strongly than and blocks oxygen transport

Answer: D

CO has a much higher affinity for haem iron than , forming carboxyhaemoglobin and preventing oxygen delivery. The iron stays in the +2 state, so oxidation to methaemoglobin is not the mechanism.
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