A buffer solution is a solution which has the ability to maintain its pH when acids or bases are added to it.
The pH of a given solution can be easily altered by the addition of acids or bases.
Buffers are defined as the solutions which resist change in pH by the addition of small amounts of acids or bases. A buffer usually consists of a weak acid and its salt (e.g. acetic acid and sodium acetate) or a weak base and its salt (e.g Ammonium hydroxide and ammonium chloride). Several buffers can be prepared in the laboratory. Nature has provided many buffers in the living system.
The internal pH of most living cells is close to 7. Even a slight change in pH can be harmful, because the chemical processes of the cell are very sensitive to the concentrations of hydrogen and hydroxide ions.
Bicarbonate buffer system in blood
Blood pH is regulated to stay within the narrow range of 7.35 to 7.45, making it slightly alkaline.
Bones are especially affected by blood pH as they tend to be used as a mineral source for pH buffering.
The presence of buffers in biological fluids allows for a relatively constant pH despite the addition of acids or bases. Buffers are substances that minimize changes in the concentrations of H+ and OH− in a solution. For example, buffers normally maintain the pH of human blood very close to 7.4, which is slightly basic. A person cannot survive for more than a few minutes if the blood pH drops to 7 or rises to 7.8. Under normal circumstances, the buffering capacity of the blood prevents such swings in pH.
A buffer works by accepting hydrogen ions from the solution when they are in excess and donating hydrogen
ions to the solution when they have been depleted. Most buffer solutions contain a weak acid and its corresponding base,
which combine reversibly with hydrogen ions. There are several buffers that contribute to pH stability in human blood
and many other biological solutions. One of these is carbonic acid (H2CO3), which, as already mentioned,
dissociates to yield a bicarbonate ion (HCO3−) and a hydrogen ion (H+):
The chemical equilibrium between carbonic acid and bicarbonate acts as a pH regulator, the reaction shifting left or right as other processes in the solution add or remove hydrogen ions. One example of a buffer solution found in nature is blood.