Hemoglobin (abbreviated Hb) is a protein that is responsible for the transport o

Question

Hemoglobin (abbreviated Hb) is a protein that is responsible for the transport of oxygen in the blood of mammals. Each hemoglobin molecule contains four iron atoms that serve as the binding sites for O_2 molecules. The oxygen binding is pH dependent. The relevant equilibrium reaction is: HbH_4^4+ (aq) + 4O_2(g) rightwardsharpoonoverleftwardsharpoon Hb(O_2)_4(aq) + 4H^+ (aq). Use Le Chatelier's Principle to answer the following: What form of hemoglobin, HbH_4^4+ or Hb(O_2)_4, is favored in the lungs? What form is favored in the cells? When a person has suffered a cardiac arrest, an injection of a sodium bicarbonate solution is given. Why is this step necessary?

Explanation / Answer

The equilibrium reaction for the transport of oxygen by haemoglobin (Hb) can be represented as:

HbH4+ + 4O2 -----> Hb(O2)4 + 4H+

In the lungs where there is a high concentration of oxygen, by Le Chatelier's principle the equilibrium position shifts to the right resulting in the formation of oxyhaemoglobin. I.e.Hb(O2)4

In tissues the concentration of oxygen is lower, so the equilibrium position shifts to the left, by Le Chatelier's principle. Oxyhaemoglobin releases oxygen to re-form haemoglobin. HbH4+

B) hemoglobin has more affinity for oxygen at higher pH. Hence at the time of cardiac arrest injection of sodium bicarbonate provide higher or alkaline pH which causes more transport of oxygen.

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