Question

D. On the surface of red blood cells there is a passive antiporter than moves bicarbonate and chloride ions in oppòsite directions. Bicarbonate is produced from carbon dioxide and water by the activity of an enzyme called carbonic anhydrase. Chloride as well as several other inorganíc ions have been shown to reduce oxygen affinity by hemoglobin when these anions are bound to the central cavity Why is it important that this transporter is an antiporter? In what circumstances will bicarbonate move out of the red blood cell? By what mechanism will chloride reduce oxygen affinity? Why does influx of chloride in this circumstance make some biological sense?

Answer 1

• The antiporter of the cardiovascular system is the exchange of bicarbonate and chloride in the blood plasma membrane. RBCs exchange bicarbonate for chloride ions using an anion exchanger. Rise in intracellular bicarbonate leads to bicarbonate to pump out resultion influx of chloride ions whixh lowers the systemic venuos blood.
• The capacity of blood to carry carbon dioxide as biocarbonate is enhanced by an transport system that makes bicarbonate move out of the plasma membrane of RNC in exchange of chloride ions. The inflow of the chloride ions retains the cells electric neutrality.
• This chloride exchange occurs and this directly affacts the affinity of oxgen in Hb. The chloride ions habe allosteric effect on hemoglobin which causes it to a decreased affinity and an increase in alkaline Bohr Effect. This results in shifting of the ocygen dissociation curve. This means the affinity of oxgen to Hb in inversely proportional to ionic concentration of chloride ions.
• Influx of chloride ions lowers the level of venous blood than the arterial blood level. This is oxygenation od the deoxygenated blood present in venous blood.