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Bicarbonate

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Bicarbonate is a vital chemical substance used in biology and chemistry. In inorganic chemistry, it is known as hydrogencarbonate. It is a polyatomic anion, which is a group of atoms with a negative charge. Its chemical formula is HCO3−. This ion is an intermediate form during the deprotonation of carbonic acid. This means it forms when carbonic acid loses a hydrogen ion. Bicarbonate is important because it helps regulate pH levels in many systems.

Riassorbimento bicarbonati e respirazione cellulare
Riassorbimento bicarbonati e respirazione cellulare

The structure of the bicarbonate ion is very specific. It has a molecular mass of 61.01 daltons. At its center sits one carbon atom. Three oxygen atoms surround this central carbon in a trigonal planar arrangement. This means the atoms lie flat on a single plane. One hydrogen atom is also attached to one of those oxygen atoms. The ion carries a negative one formal charge. It is also an amphiprotic species. This term describes a substance that can act as both an acid and a base. It can donate a proton to become a carbonate ion, or accept one to become carbonic acid.

Bicarbonate plays a massive role in human physiology through pH buffering. A buffer is a system that resists changes in acidity or alkalinity. In the human body, 70% to 75% of bicarbonate is converted into carbonic acid. This acid can quickly turn back into bicarbonate. This creates a volatile equilibrium with water, hydrogen ions, and carbon dioxide. This system protects tissues, especially in the central nervous system. If pH levels move too far outside the normal range, it can lead to acidosis or alkalosis. These conditions can be disastrous for the body.

Reference ranges for blood tests - by molarity
Reference ranges for blood tests - by molarity

The body moves bicarbonate through several complex biological processes. Inside the mitochondria, the oxidation of sugars produces carbon dioxide as a waste product. This carbon dioxide reacts with water. An enzyme called carbonic anhydrase catalyzes this reaction to form carbonic acid. This acid is in equilibrium with the bicarbonate ion. The bicarbonate is then carried through the blood to the lungs. At the lungs, the reaction reverses and the gas is released. The kidneys also help manage these levels. Cells lining the proximal tubule in the kidney transport bicarbonate from the glomerular filtrate back into the blood.

Bicarbonate is also essential for a healthy digestive system. After food is digested by highly acidic juices in the stomach, the pH must be managed. The pancreas releases bicarbonate in response to a hormone called secretin. This release neutralizes the acidic chyme, which is the semi-fluid mass of partly digested food. This process occurs as the chyme enters the duodenum, the first part of the small intestine. This helps regulate the pH of the small intestine so digestion can continue safely.

In the natural world, bicarbonate is a major part of the carbon cycle. It is the dominant form of dissolved inorganic carbon in seawater and most fresh waters. This makes it a significant sink for carbon. Some plants, such as Chara, use carbonate to produce calcium carbonate through biological metabolism. In freshwater ecology, photosynthesis can change the chemistry of the water. During daylight, photosynthetic activity releases oxygen and produces bicarbonate ions. This can shift the pH upward. In darkness, respiration processes release carbon dioxide. This leads to a rapid fall in pH.

Humans use bicarbonate in many everyday ways. The most common salt is sodium bicarbonate, known as baking soda. When heated or mixed with an acid like vinegar, it releases carbon dioxide gas. This gas acts as a leavening agent to make bread rise. Ammonium bicarbonate is another salt used to manufacture cookies, crackers, and biscuits. In medicine, doctors use bicarbonate to check health. They measure bicarbonate levels in an electrolyte panel test. This is done alongside chloride, potassium, and sodium to assess acid-base physiology.

Reference ranges for blood tests - by molarity
Reference ranges for blood tests - by molarity
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