Functions of Buffer in Human

A buffer solution consists of a mixture of a week acid and its conjugate base. Buffer solutions tend to resists a change in pH on the addition of moderate amounts of strong acid or base. Buffers help to maintain the intracellular fluids of all organisms at characteristic and fixed pH values. The influence of pH on physiological function is the pH of blood must be maintained at 7.4. If the pH rises above 7.7, blood cannot release carbon dioxide to the lungs and if it falls below 7.3, blood cannot remove carbon dioxide from other tissues.

Low blood pH, or called acidosis, is caused by diabetes, starvation, kidney disease, or respiratory disease. If acidosis is not treated promptly, the affected individual may go into a coma and die. The pH of blood can also rise to dangerously high levels. This condition called alkalosis, can be caused by hyperventilation, the excessively deep and rapid breathing. This condition also brough by prolonged vomiting or by ingestion of excessive amounts of alkaline drugs, which overexcites the central nervous system.As with all proteins, hemoglobin’s conformation is sensitive to a variety of factors. For example, a drop in pH lowers the affinity of hemoglobin for O2, an effect called the Bohr shift. Because CO2 reacts with water, forming carbonic acid (H2CO3), an active tissue lowers the pH of its surroundings and includes hemoglobin to release more O2, which can then be used for cellular respiration.

This figure is taken from Campbell, N.A. (2005). Biology, Seventh Edition.

1. Carbon dioxide produced by body tissue diffuses into the interstitial fluid and the plasma.

Over 90% of the CO2 diffuses onto red blood cells, leaving 7% in the plasma as dissolved CO2.

2. Some CO2 is picked up and transported by hemoglobin.

3. However, most CO2 reacts with water in red blood cells, forming carbonic acid (H2CO3), a reaction catalyzed by carbonic anhydrase contained within red blood cells.

4. Carbonic acid dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+).

5. Hemoglobin bind most of the H+ from H2CO3, preventing the H+ from acidifying the blood and thus preventing the Bohr shift.

6. If the buffer system in human body are malfunction, hemoglobin bind most of the H+ from H2CO3 , allowing the H+ from acidifying the blood and thus allowing the Bohr shift.

Application

The process of respiration plays an important role in the buffering of blood. In particular, an increasing in "H" ^+ concentration can dealt with by raising the rate of respiration. Initially, the added hydrogen ion binds to bicarbonate ion, forming carbonic acid.

An increased level of carbonic acid raises the levels of dissolved carbon dioxide in the lung.

A high respiration rate removes this excess carbon dioxide from the lungs, starting a shift in the equilibrium positions of all the foregoing reactions. The removal of gaseous CO2 decrease the amount of dissolved CO2. Hydrogen ion reacts with HCO-3 and, in the process, lower the H+ concentration of blood back to its original level. In this way, the blood pH is kept constant.

In contrast, hyperventilation removes such large amounts of carbon dioxide from the lungs that it raises the pH of blood, sometimes to dangerously high levels that bring on weakness and fainting. Athletes, however, have learned how to use the increase in blood pH caused by hyperventilation. Short bursts of strenuous exercise produce high levels of lactic acid in the blood as a result of the breakdown of glucose. The presence of so much lactic acid tends to lower the pH of the blood, but a brief (30 seconds) period of hyperventilation before a short-distance event, for example 400m dash, 100m swim, 1km bicycle race, or any event that lasts between 30 seconds and about a minute, that counteracts the effects of the added lactic acid and maintain the pH balance.

An increase in H+ in blood can be caused by a large amount of any acid entering the bloodstream. Aspirin, like lactic acid, is an acid, and extreme acidity resulting from the ingestion of large doses of aspirin poisoning. Exposure to high attitudes has an effect similar to hyperventilation at sea level. In response to the tenuous atmosphere, the rate of respiration increase. As with hyperventilation, more carbon dioxide is expired from the lungs, ultimately lowering the H+ level in blood and raising the pH. When people who normally live at sea level are suddenly placed at a high elevation, their blood pH rises temporarily, until they become acclimated.