Respiration Buffering of Acidosis - Bicarbonate

Buffering of an Acid - Bicarbonate Buffering System

There are three systems involved in preventing wide swings in blood pH. Respiration, Circulatory and Renal systems.

A goal in Homeostasis is the prevention of wide swings in chemical imbalance. The free hydrogen ion (H +) is a prime candidate to keep within the pH range of 7.38 and 7.42.

It is important to recognize the ability to have a two way system. This enables the bicarbonate buffering system to act on an acidosis one way and an alkalosis on the other way.

One factor to remember is living cells always produce carbon dioxide as a by product. Therefore there is a constant  source of carbon dioxide being formed.

The Respiratory System can control the amount of free hydrogen ion (H +) by either breathing rapidly or very slowly.

Here is the equation:

If carbon dioxide is allowed to build up in the blood by increasing its concentration from lower than normal respiration rate the equation above moves to the right.

The water (H2O) combines with the excess carbon dioxide to form undissociated carbonic acid (H2CO3) that immediately breaks down (dissociates) into free hydrogen ion (H+) and a bicarbonate ion (HCO3-). The increase in the concentration of free hydrogen ion (H+) lowers the pH (becomes more acidic).

If the acidity of the blood approaches a pH of 7.38 the reversible formula above begins to move to the left.

The excess of free hydrogen ion (H+) combines with the bicarbonate ion (HCO3-) to form carbonic acid (H2CO3) that immediately breaks down into water (H2O) and carbon dioxide (CO2).

This happens because the Respiratory System is breathing at a faster rate than normal and "blows off" the excess carbon dioxide (CO2). 

This temporarily takes free hydrogen ion (H+) out of circulation and the pH moves to a more alkaline pH of 7.42.

In a nutshell this is the Bicarbonate Buffering System.

This process continues without your knowledge as a state of equilibrium is maintained that keeps the pH in the range of 7.38 to 7.42.