Question

Carbon monoxide is posionous because it ?

• A. Dries up
• B. Reduces the organic matter of tissues
• C. Combines with haemoglobin and causes
  deficiency of oxygen in blood
• D. Combines with the
  $O_2$ present in blood to form
  $C{O}_2$

Answer 1

The correct option is C Combines with haemoglobin and causes

deficiency of oxygen in blood
Due to the formation of a stable compound called carboxyhaemoglobin on reaction of carbon-monoxide with haemoglobin. The haemoglobin is no longer useful for carrying oxygen and Hb has 250 times more affinity to combine with CO as compare to O2. When a substantial amount of haemoglobin becomes useless, the availability of oxygen to the tissues is reduced which is dangerous.