In the last lesson I talked about the importance of maintaining body fluids, and briefly discussed the role of solutes (including electrolytes) in maintaining fluid balance. So what are electrolytes and why do we call them electrolytes anyway? Electrolytes are simply ions in solution. As you might remember, ions are charged and are therefore able to carry an electrical current.  Hence we call them electrolytes. They include the following ions:

  1. Sodium (Na+)
  2. Potassium (K+)
  3. Calcium (Ca2+)
  4. Chloride (Cl-)
  5. Magnesium (Mg2+)
  6. Phosphate (PO43-)
  7. Bicarbonate (HCO3-)

In this lesson I will only be talking about the role of HCO3- in pH regulation and the role of Na+ and K+ in nerve impulse control.

pH Regulation 

Blood pH must be kept between 7.35 to 7.45 to avoid acidosis and alkalosis respectively. This is because enzymes and proteins which are integral to various metabolic processes are very sensitive to pH. If the pH is too high or too low they become denatured and no longer able to carry out their function. In order to control pH the body uses different strategies.

Strategy 1: The Bicarbonate Buffer System

One of the main blood buffers in the Bicarbonate Buffer System. Carbondioxide produced in energy production dissolves into the blood to form carbonic acid. Carbonic acid dissociates into hydrogen and bicarbonate ion. This is a reversible reaction as shown in the diagram below. If the blood encounters acidic compounds, some of the acid will be “mobbed up” by the bicarbonate base, softening the blow of the acid and hence preventing any major shift in pH. On the other hand, let’s say the blood is exposed to basic compounds. The bases would be “mopped up” by the hydrogen ions, hence softening the blow of the base and reducing shifts in pH. 

Strategy 2: Respiratory Compensation

In case acid levels are still too high, we can get rid of excess carbondioxide by heavy and rapid breathing (hyperventilation). This reduces the amount of acid in the blood by forcing the reaction to the left.

Strategy 3: Renal Compensation

Further control of pH can be done with the help of the kidney if the above strategies are inadequate. For example, the kidney can dump bicarbonate ions into the blood if it because too acidic, or secrete bicarbonate ions out of the blood if it becomes too basic. 

Reference: Thompson,&  J., Manore, M., Vaughan, L. (2020). The science of nutrition (5th ed.). New York. Pearson

Courtney Simons
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Courtney Simons is a food science professor. He holds a BS degree in food science and a PhD in cereal science from North Dakota State University.
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