The Buffer System

The buffer system is apart of the acid-base balance. The body needs to balance the pH in the plasma to within 0.10 degrees of 7.35 to 7.45pH to remain in homeostasis, which is 7.40pH. The pH system was devised from a Danish biochemist by the name of Soren Sorensen in 1909 for the use in the making of beer. The symbol pH stands for parts of hydrogen per liter of fluid. The problem was that the beer was spoiling due to the growth of bacteria in the beer. Sorensen discovered that by decreasing the pH balance, which would make the beer more acidic the bacteria, would not be able to grow/live in this environment. We have found through Sorensen work that the body like the bacteria is very sensitive to slight changes in the blood plasma.

The many cells of the body require that the pH stay within this perimeter to maintain homeostasis. The three parts of the buffer system include, chemical buffering mechanisms, which consist of (bicarbonate, phosphate, and protein buffer system), the kidneys, and the lungs. The pH is defined as hydrogen ion concentration; the more hydrogen ions, the more acidic the solution will become.

Chemical buffering are substances that prevent major changes in the pH of the body's fluids by removing or releasing hydrogen ions. They can act within a fraction of a second to prevent excessive changes in the hydrogen ion concentration (Metheny, 1996, pg 159). The main buffering system is the bicarbonate (HCO3)-carbonic acid (H2CO3) buffer system. The bicarbonate to hydrogen is 20:1 it will take 20 parts of bicarbonate to neutralize 1 part hydrogen ion. If either bicarbonate or carbonic acid is increased or decreased so that the 20:1 ratio is no longer valid, acid-base imbalance results.

Other less important buffer systems in the extracellular fluid includes the inorganic phosphates and the plasma proteins. Intracellular buffers include proteins, organic and inorganic phosphates, and, in red blood cells, hemoglobin (Metheny, 1996,pg 160).

The kidneys regulate the bicarbonate level in the extracellular fluid; they are able to regulate bicarbonate ions as well as reabsorb them from the renal tubular cells. In the case of respiratory and metabolic acidosis the kidneys will excrete hydrogen ions in the urine and conserve bicarbonate ions to help restore balance, in the case of respiratory and metabolic alkalosis the kidneys will excrete bicarbonate in the urine and conserve the hydrogen ions to help restore balance. This is a slower process and will take hours to days instead of seconds as with the chemical (carbonic acid) buffer system.

Under the influence of the respiratory center (chemo-receptors) in the aorta arch and in the carotid body, the lungs control the CO2 (and thus the carbonic acid) content of the extracellular fluid by adjusting ventilation in response to the amount of CO2 and, to lesser extent, oxygen in the blood (Metheny, 1996, pg 160). The carbonic acid formula is H2CO3 and as the hydrogen ions increase in the blood the free hydrogen ion will bond to the bicarbonate ion HCO3-, this will form carbonic acid and the end result will be H2O AND CO2 (water and carbon dioxide).

The production of acid in the body happens in many different ways 1) break down of phosphorus-containing proteins release phosphoric acid in to the extracellular fluid, 2) anaerobic respiration of glucose produces lactic acid, 3) fat metabolism yields ketones, 4) the loading of carbon dioxide in the blood will release hydrogen ions (Marieb, 2001, pg1055).