In: Chemistry
A buffer is mixture of weak acid (base) and the salt of its conjugate base (acid).
Acidic buffer: CH3COOH (weak acid) + CH3COONa
CH3COO- is the conjugate base of CH3COOH
Basic buffer: NH3 (weak base) + NH4Cl (NH4+ is the conjugate acid of NH3).
A buffer can resist small changes in the H+ and OH- concentrations thereby maintaining a constant value of pH of the system.
Breathing or respiration is based on carbonic acid-bicarbonate buffer system which can be shown by the following equilibrium equation:
CO2 (g) + H2O (l) <------> H+ (l) + HCO3- (l)
Respiratory and urinary systems helps in compensating the pH. Increase in H+ drives the equilibrium to the left forming more carbondioxide which is eliminated by lungs and urinary system is responsible for bicarbonate levels in the blood.