Q.

Which of the following is an example of buffer system in blood
 a) Haemoglobin and oxyhaemoglobin                 b)    Oxygen and carbon dioxide
 c) Albumin and globulin                                        d)    Sodium bicarbonate and carbonic acid

AA
BB
CC
DD

A.

(d) A buffer is a chemical or combination of chemicals that can both take up and release hydrogen ions. Carbonic acid (H_2 CO_3) and sodium bicarbonate (NaHCO_3) help buffering human blood because H_2 CO_3 is a weak acid that does not totally dissociate, when excess hydrogen ions are present in blood, the reaction goes to the left and carbonic acid forms to maintain the pH.
     H_2 CO_3               ?              H^+        +             HCO_3^-
Carbonic acid            Hydrogen ion        Bicarbonate ion 

 



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