Bicarbonates are common chemical compounds found throughout nature and within living organisms. They are negatively charged ions, carrying an electrical charge. These ions play a fundamental role in various chemical and biological processes. Their presence is fundamental to many systems, from oceans to the intricate chemistry within the human body.
Chemical Identity
The bicarbonate ion is represented by the chemical formula HCO3-. It consists of a central carbon atom bonded to three oxygen atoms, with one also attached to a hydrogen atom. This structure gives the ion a net negative charge.
Bicarbonates primarily form from the dissociation of carbonic acid (H2CO3) when it dissolves in water. Carbonic acid forms when carbon dioxide (CO2) dissolves in water. This reversible reaction allows for a dynamic balance between carbon dioxide, carbonic acid, and bicarbonate ions. The bicarbonate ion acts as a weak base, capable of accepting or donating a proton (hydrogen ion). This allows bicarbonates to participate in buffering systems, moderating changes in acidity or alkalinity.
Essential Roles in the Human Body
Bicarbonate plays a central role in maintaining the body’s pH balance. The bicarbonate buffer system is the primary mechanism for keeping blood pH within a healthy range, typically around 7.4. This system involves a continuous interplay between carbonic acid, bicarbonate ions, and carbon dioxide. When excess acid enters the bloodstream, bicarbonate ions neutralize it by forming carbonic acid, which then dissociates into carbon dioxide and water.
The lungs quickly adjust blood pH by altering the rate at which carbon dioxide is exhaled. If blood becomes too acidic, breathing speeds up to expel more CO2, shifting the equilibrium to reduce acidity. Conversely, if blood becomes too alkaline, breathing slows down to retain CO2.
The kidneys also contribute to long-term pH regulation by controlling bicarbonate levels. They can reabsorb bicarbonate back into the blood or excrete it in urine, depending on the body’s needs. This dual regulation by the respiratory and renal systems ensures that blood pH remains stable, allowing enzymes and physiological processes to function correctly.
Beyond pH regulation in the blood, bicarbonates are also important for digestion. The pancreas secretes bicarbonate-rich fluid into the duodenum, the first section of the small intestine. This secretion neutralizes the acidic chyme that enters from the stomach, protecting the duodenal lining from acid damage. Neutralizing the chyme also creates an optimal pH environment for digestive enzymes to function effectively, for proper nutrient breakdown and absorption.
Beyond the Body: Natural Occurrence and Uses
Bicarbonates are found in natural environments beyond biological systems. They are a significant component of natural waters, contributing to “hard water.” In oceans, bicarbonates are the dominant form of dissolved inorganic carbon and play a central role in the global carbon cycle. Atmospheric carbon dioxide dissolves into ocean water, forming carbonic acid, which then dissociates into bicarbonate ions. This process impacts ocean pH and influences marine life, especially organisms that build shells from calcium carbonate.
Bicarbonates also occur naturally in mineral deposits, such as nahcolite and trona. These sources are mined for various applications. Sodium bicarbonate, commonly known as baking soda, is a form of bicarbonate. It is used as a leavening agent in baking, reacting to produce carbon dioxide gas, causing dough to rise.
Sodium bicarbonate functions as an antacid, neutralizing stomach acid to relieve indigestion. It is also employed as a deodorizer, absorbing odors, and is a component in some dry-chemical fire extinguishers, releasing carbon dioxide to smother flames. Other uses include effervescent tablets and various cleaning products.