Question

Assertion: Chloride shift is the exchange of $C{{l}^{-}}$ of plasma and $HCO_{3}^{-}$ RBC’s.
Reason: The chloride shift maintains an acid-base balance between the RBCs and plasma.
A) Both assertion and reason are correct and the reason is the correct explanation for the assertion.
B) Both assertion and reason are correct but the reason is not the correct explanation for the assertion.
C) The assertion is correct but the reason is incorrect
D) Both assertion and reason are incorrect.

Answer 1

Hint:Red blood cells or RBCs or erythrocytes are red coloured cells which are found in our body and have a major role in transport of oxygen all throughout the body. Chloride shift is seen in RBCs.

Complete answer:
Let us first know about chloride shift before we move ahead. CHloride shift can be defined as the process by which chloride ions present in the plasma move into the RBCs as the blood experiences a transition from arterial to venous gas. It is also known as Hamburger shift.

The steps in chloride shift are as follows
i) The chloride $\left( C{{l}_{2}} \right)$ ions move into the RBCs and the bicarbonate$(HCO_{3}^{-})$ ion moves out into the venous blood.
ii) Then, the carbon dioxide $(C{{O}_{2}})$ diffuses into the red cells.
iii) The carbon dioxide is converted into bicarbonate by an enzyme called carbonic anhydrase.
iv) The bicarbonate is pumped out of the red cells and then chloride is pumped into it.
v) The entire process happens very quickly.

Now, the reverse of these events take place in the pulmonary capillaries. The bicarbonate is pumped back into the red cells and the chloride is then pumped out . Carbonic acid $({{H}_{2}}C{{O}_{3}})$ then readily dissociates into hydrogen ions \[({{H}^{+}})\] and hydrogen carbonate ions $(HCO_{3}^{-})$. $HCO_{3}^{-}$ ions diffuse out the RBCs into the plasma where they combine with Na+ ions from the dissociation of sodium chloride to form sodium hydrogen carbonate $(NaHC{{O}_{3}})$. To balance the outward movement of negatively charged $HCO_{3}^{-}$ ions, chloride $(C{{l}^{-}})$ ions diffuse in.

Therefore, the correct option is (A) Both assertion and reason are correct and the reason is the correct explanation for the assertion.

Note: The significance of chloride shift is as follows,
i) It ensures that there is no buildup of electric charges during gaseous exchange.
ii) It helps in excretion of carbon dioxide from the blood.
iii) It allows plasma to act as a storage site for bicarbonate without changing the electrical charge of both plasma and RBC.