Clinical Correlates of pH Levels
Problem Set

Problem 2: Bicarbonate as a biological buffer

Bicarbonate is a crucial buffer in the body and is usually present in body fluids as sodium bicarbonate (sodium being the main positive ion in extracellular fluids). What features of sodium bicarbonate contribute to its effectiveness as a biological buffer?

A.	The bicarbonate ion (HCO3-) can combine with a proton (H+) to form carbonic acid (H2CO3), thus absorbing protons from solution and raising blood pH.
B.	Carbonic acid, which can be formed from CO2 and water, can dissociate into H+ and HCO3- in order to provide H+ and lower blood pH.
C.	Carbonic acid, which can be formed from bicarbonate, is converted to CO2 and water via a very fast enzymatic reaction.
D.	CO2, being volatile, can be rapidly expelled from the body at varying rates by respiration.