This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Membrane Structure & Function, Subject name: Biochemistry
Important buffer in the extracellular fluid is: 
Select and explain. 
A. Phosphate, B. Acetate, C. Bicarbonate, D. Plasma protein
C: Bicarbonate
Answer: C: Bicarbonate 
Explanation: Ans. C. BicarbonateThe bicarbonate buffer system is the most important extracellular buffer. Although it has a relatively low buffering capacity with pKa 6.3, it plays an important role in maintaining blood pH because1. Of its high concentration 2. The two elements, HCO3- and CO2 of H2CO3 are regulated by increasing or decreasing the rate of reabsorption of HCO3- by the kidneys and by altering the rates of removal or retention of CO2.