Respiration and Circulation — BIOLOGY STD 12 Science — Question
Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYRespiration and Circulation4 Marks
Question
Chloride shift or Hamburger’s phenomenon.
✓
Answer
$1.$About $70\%$ of $CO_2$ is transported in the form of sodium bicarbonates/potassium bicarbonates from tissue cells to lungs.
$2.$ In the $\text{RBCs}, \ CO_2$ combines with water in the presence of a $Zn$ containing enzyme, carbonic anhydrase to form carbonic acid. This action is rapid in $\text{RBCs}$ as compared to that in the plasma.
$3.$Carbonic acid being unstable, immediately dissociates into $HCO_3^–$ and $H^+$ in the presence of same enzyme, leading to large accumulation of $HCO_3^– $ inside the $\text{RBCs}$. It thus moves out of $\text{RBCs}$. This can bring about imbalance of the charge inside the $\text{RBCs}$.
$4.$To maintain the ionic balance between the $\text{RBCs}$ and the plasma, $Cl^–$ diffuses into the $\text{RBCs}$. This movement of chloride ions is known as chloride shift or Hamburger’s phenomenon.
$5. \ HCO_3^–$ that comes in the plasma joins to $Na^+/K^+$ forming $NaHCO_3/KHCO_3$ which can maintain pH of blood. The remaining $H^+$ ions in the $\text{RBCs}$ are buffered by haemoglobin by the formation of oxyhaemoglobin.
$6.$ At the level of lungs, due to the low partial pressure of carbon dioxide of the alveolar air, hydrogen ion and bicarbonate ions combine to form carbonic acid and under the influence of carbonic anhydrase again yields carbon dioxide and water.
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