formation of hydrogencarbonate ions

• carbon dioxide in the blood plamsa diffuses int other red blood cells. here it combines with water to form a weak acid called carbonic acid.
• The formation of carbonic acid is catalysed by the enzyme called carbonic anhydrase.

  Carbon dioxide (C O 2 ) + Water (H 2 O) > Carbonic acid (H 2 C O 3)
• Carbonic acid dissociates to release Hydrogen Ions (H +) and hydrogencarbonate ions (HCO3 - ):

  Carbonic acid (H 2 C O 3) > Hydrogencarbonate ion (H C O 3 - ) + hydrogen ion (H + )
• the hydrogen carbonate ions diffuse out of the red blood cells into the plasma. the charge inside the red blood cells is maintained by the movement of chloride ions from the plasma into the red blood cell known as the chloride shift.
• The hydrogen ion build up in the red blood cell could cause the contents of the red blood cell to become very acidic. To prevent this, hydrogen ions are taken out of solution by associating them with haemoglobin to form haemoglobinic acid ( HHb). The haemoglobin is acting as a buffer.