CO-Hb bond is:
Correct answer: A. More stable than O2-Hb bond.
- A. More stable than O2-Hb bond.
- B. Less stable than O2-Hb bond
- C. Stability of both bonds are approximately same
- D. CO-Hb does not exist
Explanation
The CO-Hb bond is more stable than the O2-Hb bond because of the following reasons: CO has a higher affinity for hemoglobin than O2 does. Theaffinity of CO for hemoglobin is approximately 200 times greater than that of O2. The CO-Hb bond can not be reversed because it forms a stable complex called carboxyhemoglobin, whereas the O2-Hb bond can be easily reversed because it forms a reversible complex called oxyhemoglobin. The stability of the CO-Hb bond arises from the fact that CO binds to the heme group in hemoglobin with a bond order of 3, which is stronger than the bond order of 2 for O2. Carboxyhaemoglobin is about 300 times more stable than oxyhemoglobin due to back bonding and formation of metal-ligand pi bond.
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