urée

Urea, known in French as urée, has the chemical formula CO(NH2)2 and is a colorless, highly soluble organic compound. It is the principal nitrogen-containing waste product of protein metabolism in many organisms and a major constituent of urine. In humans and many mammals, urea is synthesized in the liver through the urea cycle, converting ammonia and carbon dioxide into urea, which is then transported to the kidneys for excretion.

Biology and metabolism: In the liver, ammonia produced from amino acid breakdown is detoxified by converting it into urea via a series of enzymatic steps involving several key enzymes. Urea is released into the bloodstream, filtered by the kidneys, and eliminated in urine. Disruptions of the urea cycle can lead to elevated ammonia levels and metabolic disorders.

Industrial production and uses: Urea is manufactured on a large scale from ammonia and carbon dioxide under high pressure and temperature in the Bosch-Meiser process. The resulting product is typically used in aqueous solutions that are concentrated and crystallized. It is the most widely used nitrogen fertilizer due to its high nitrogen content (about 46% by weight) and water solubility, and it serves as a raw material for resins, polyurethanes, plastics, and various polymers.

Applications and analysis: In agriculture, urea provides nitrogen to plants. In medicine and cosmetics, urea is used as a keratolytic agent and humectant. In clinical settings, blood and urine urea measurements (urea or blood urea nitrogen) are common indicators of kidney function and protein intake.

See also: Uric acid, urea cycle, Bosch-Meiser process.