Bicarbonate is a naturally occurring chemical compound that plays a fundamental role in both the human body and everyday household chemistry. It exists primarily as an ion, a charged molecule that helps regulate many bodily functions. As an electrolyte, it conducts electricity when dissolved in water.
The Chemical Definition
Bicarbonate exists as a polyatomic anion, a molecule composed of multiple atoms that carries a negative electrical charge. Its chemical formula is \(HCO_3^-\), representing one central carbon atom bonded to three oxygen atoms and one hydrogen atom.
The bicarbonate ion is an intermediate form in a dynamic chemical relationship involving carbon dioxide (\(CO_2\)) and water (\(H_2O\)). When carbon dioxide dissolves in water, it first forms carbonic acid (\(H_2CO_3\)), a weak acid. Carbonic acid then rapidly dissociates to yield a hydrogen ion (\(H^+\)) and the bicarbonate ion (\(HCO_3^-\)). This reversible interconversion allows bicarbonate to function as a chemical buffer, accepting or donating hydrogen ions.
Essential Role in Maintaining pH Balance
The primary function of bicarbonate in the body is to act as the main component of the carbonic acid-bicarbonate buffer system, which maintains the blood’s delicate pH balance. The human body must keep its blood pH within a narrow range, typically between 7.35 and 7.45, for cellular processes to function correctly. Bicarbonate achieves this stability by neutralizing strong acids or bases that enter the bloodstream from metabolic processes.
If an excess of acid is introduced, the bicarbonate ions quickly bind to the free hydrogen ions (\(H^+\)) to form carbonic acid, which is a much weaker acid. Conversely, if a base enters the bloodstream, the carbonic acid in the system releases a hydrogen ion to neutralize the base. This buffering action prevents drastic shifts in the blood’s acidity.
Beyond pH regulation, bicarbonate also plays a significant role in transporting carbon dioxide, a waste product of cellular metabolism. About 70 to 75 percent of the \(CO_2\) produced by tissues is converted into bicarbonate inside red blood cells for transport to the lungs. Once the blood reaches the lungs, this chemical reaction reverses, converting the bicarbonate back into \(CO_2\) so it can be exhaled.
Measuring Bicarbonate in Clinical Tests
Bicarbonate levels in the blood are routinely measured by physicians as a marker of the body’s acid-base status and overall metabolic health. This measurement is typically performed as part of a routine blood test called an electrolyte panel or a more detailed arterial blood gas analysis. In clinical settings, the result is often reported as the total \(CO_2\) concentration, which primarily reflects the amount of bicarbonate present in the blood.
The normal concentration of bicarbonate for an adult is generally between 22 and 29 milliequivalents per liter (mEq/L). Levels outside this range indicate a metabolic disturbance requiring further investigation. A low bicarbonate level (below 22 mEq/L) signals metabolic acidosis, meaning the body has too much acid or has lost too much base. This imbalance can be caused by conditions such as severe diarrhea, uncontrolled diabetes, or kidney failure.
Conversely, a high bicarbonate level (above 29 mEq/L) suggests metabolic alkalosis, meaning the body has an excess of base or has lost too much acid. This condition is often seen in cases of prolonged vomiting, where stomach acid is lost, or from the excessive intake of certain antacids. Since the kidneys and lungs regulate bicarbonate, abnormal levels provide direct insight into the function of these organs.
Common Uses of Sodium Bicarbonate
While the bicarbonate ion is essential for health, its salt form, sodium bicarbonate (baking soda), is a common household compound. It is utilized for its chemical property as a mild base. One recognized use is as a leavening agent in baking: when exposed to heat or combined with an acidic ingredient, it releases carbon dioxide gas, causing doughs to rise.
The compound is also widely used as an over-the-counter antacid to treat heartburn and indigestion. When ingested, the basic sodium bicarbonate neutralizes the highly acidic hydrochloric acid in the stomach. This reaction produces a salt, water, and carbon dioxide gas, which rapidly relieves the discomfort associated with acid reflux.
Its mild alkaline nature also makes it useful for household applications, such as a deodorizer and a gentle cleaning abrasive. By neutralizing acidic compounds that cause odors, sodium bicarbonate helps to eliminate smells rather than just masking them.