Question

Q.2 [8 marks]
Discuss the cooperative effect that occurs when haemoglobin binds or releases oxygen.

Answer 1

Haemoglobin is a red coloured iron containing pigment in the RBCs. it has four polypeptide chain and therefore has a quaternary structure. each polypeptide chain possesses a globin polypeptide chain that is linked to a heam group, which is responsible for the characteristic red colour of the blood , an iron atom is located within each heam group .O_{2 CAN BIND WITH HAEMOGLOBIN} Mmolecule can carry a maximum of four molecules of O₂. BINDING of oxygen with haemoglobin is primarily related to partial pressure of O_2.. Partial pressure of CO₂ , HYDROGEN ion concentration and temperature are the other factor which can interfere with this binding . a sigmoid curve is obtained when % percentage saturation of haemoglobin with O₂ is plotted against the pO_{2. THIS CURVE IS CALLED THE OXYGEN DISSOCIATION CURVE AND IS HIGHLY USEFUL IN STUDING THE EFFECT OF FACTORS LIKE} pCO₂, H+ CONCENTRATION etc on binding of O₂ WITH HAEMOGLOBIN . IN THE ALVEEOLI WHERE THERE IS HIGH pO_2, pCO_2, LESSER H+ CONCENTRATION AND LOWER TEMPRATURE the factors are all favourable for the formation of oxyhaemoglobin whereas in the tissues where low pO_2, pCO₂, HIGH H+ CONCENTRATION AND HIGHER temprature exist, the conditions are favourable for dissociation of oxygen from the oxyhaemoglobin . this clearly indicates that O₂ GETS BOUND TO HAEMOGLOBIN IN THE LUNG SURFACE AND GETS DISSOCIATED AT THE TISSUES. every 100 ml of oxygenated blood can delivere around 5ml of O₂ TO THE TISSUES UNDER NORMAL PHYSIOLOGICAL CONDATIONS.