Question

Describe the relationship between the partial pressure of oxygen and the binding of oxygen to hemoglobin.

Answer 1

At certain partial pressure of O2 binding of oxygen to hemoglobin is more and at certain partial pressure of O2 oxygen is unloaded from hemoglobin, this can be explained by oxygen dissociation curve. In ODC the ability of hemoglobin to load and unload oxygen is shown.  

OXYGEN DISSOCIATION CURVE:

partial pressure of oxygen at pulmonary alveoli is 100 the oxygen saturation of hemoglobin is 97% , increasing the partial pressure of oxygen above 60 mmhg will not increase hemoglobin saturation of oxygen and a plateau phase will be seen .

At tissue capillaries partial pressure of oxygen is 40mm hg here oxy saturation to hb is only 70% . Thus oxygen will be unloaded from hb .

P50 is where hemoglobin is 50% saturated with oxygen. In health adult p50 of blood occurs at po2 of 27mmhg . During any pathalogical conditions Po2 of oxygen has to be increased to attain 50% saturation, this will push the curve towards right side.  

CONDITIONS WHICH CAUSES SHIFT IN THE CURVE:

Effect of ph and CO2 :

In tissue capillaries, metabolic activity is high which causes increased co2 and formation of lactic acid which causes low ph , so the curve shift towards right which indicates increased unloading of oxygen by hemoglobin.  

In lungs ph is high and pco2 is low which causes left shift of the curve.  

The effect of ph and pco2 to cause loading and unloading of oxygen by hemoglobin is called bohrs effect. When pco2 level is increased , carbon dioxide will diffuse through rbc and with the help of carbonic anhydrase carbonic acid is formed wich decreases ph level and decreases oxygen affinity to hemoglobin.  

EFFECT OF TEMPERATURE AND 2, 3 BPG :

increased temperature and BPG will cause right shift of the curve , decreased temperature and decrease BPG will cause left shift . BPG is bisphosphoglycerate . This will bind with deoxygenated hemoglobin and stabilize its T configuration.