CHLORIDE SHIFT :::
The membrane of red blood cells is not permeable to K+ and Na+ but ions like HCO3 and Cl- can pass
through when CO2 enters the blood H2CO3 is formed with the help of enzyme carbonic-anhydrase (CA) This reacts with KHbO2 to liberate O2 which diffuses out in plasma and hence to the tissues Haemoglobin is reduced to HHb and during this period K+ and HCO3-ions are formed HCO3- Diffuses out to plasma where it combines with NaCl to form NaHCO3 and Cl- is set free
This Cl- is shifted to red blood cell and combines with K+ to from KCl
In the alveoli of lungs O2 enters the blood and combines with reduced haemoglobin to form HHbO2 This reacts with KCl to from KHb+O2 while H+ and Cl- ions are set free This Cl- is shifted to plasma where it reacts with NaHCO3 to from NaCl and displaces HCO3 These bicarbonate ions diffuse into red blood cell to combine with H+ ions and from H2CO3 Carbonic acid (H2CO3) Dissociates into H2O and CO2 which diffuse out in the plasma and from there to the air
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