Urea CO(NH2)2, also known as carbamide, is an essential organic compound and waste product in urine. Formed in the liver, urea is an important nitrogen-containing substance in biochemistry. Urea has a range of essential functions and applications in nature and industry.
What is Urea?
Composed of carbon, nitrogen, oxygen, and hydrogen, urea is a major nitrogenous waste product in animal metabolism. It forms in the liver when proteins break down and is primarily excreted with urine. Urea is a colorless, odorless, and highly soluble substance.
Urea contains around 46.7% nitrogen by weight, making it valuable in agriculture as a fertilizer. Farmers often use urea to boost crop yields, resulting in production increases of up 50%.
In pure form, urea is colorless and odorless. It's highly soluble in water. Its structure consists of two amine groups (NH2) connected by a carbonyl functional group (C=O), which gives it its unique properties.
Chemical / Scientific Properties of Urea
Molecular weight: 60.06 g/mol
Melting Point: 132.7 °C (271 °F)
Boiling Point: 180 °C (356 °F)
Solubility: Highly soluble in water, with a solubility of about 1 g/mL at 20 °C
Density: 1.335 g/cm³
Chemically, urea can participate in various reactions, making it a versatile substance. It can hydrolyze to form ammonia and carbon dioxide, which is an important reaction in soil chemistry for nitrogen recycling.
Discovery of Urea
Urea is first discovered in 1773 by Dutch chemist Herman Boerhaave. In 1828 German chemist Friedrich Wöhler synthesizes it from ammonium cyanate.
Wöhler's synthesis disproves the vitalism theory, which states organic compounds can be created only by living organisms. This event is often cited as the founding moment of modern organic chemistry.
Is Urea the Same as Uric Acid?
While both urea and uric acid are nitrogen-containing compounds involved in the excretion of waste from the body, they are not the same. Urea is the primary nitrogenous waste product in mammals and is highly soluble in water, allowing for easy excretion in urine.
Uric acid, on the other hand, is less soluble and is the end product of purine metabolism. It is excreted in a semi-solid form by animals like birds and reptiles, which helps conserve water in arid environments. Uric acid can form crystals as in health issues such as gout.
Humans primarily produce urea, while birds and reptiles predominantly excrete uric acid. This distinction is advantageous in arid environments as uric acid's lower toxicity allows for more efficient water retention.
Uric acid is initially discovered by the ancient Egyptians in 2640 BCE. Greek physician Hippocrates (460-370 BCE) associates gout with excess of one of the four bodily humors, phlegm, causing painful joint symptoms.
Gout is caused by uric acid crystallization in the joints. Hippocrates is also the originator of the Four Humors theory purveyed by Galen.
What is Urea’s Function in Nature?
Nitrogen Source
Urea is a major source of nitrogen for plants. Microorganisms convert urea into ammonia and nitrates, making nitrogen available for flora. This process enhances soil health and supports agricultural ecosystems.
When applied as a fertilizer, it undergoes hydrolysis in the soil to release ammonia. Plants can then uptake ammonia to synthesize essential amino acids and proteins.
Waste Excretion
For mammals, urea is a key product of amino acid breakdown, allowing the body to excrete excess nitrogen safely in a soluble form. Excretion of waste is vital to maintaining nitrogen balance and preventing toxic buildup from protein breakdown.
Historical Uses of Urea
Historically, it's primarily used in the medical field as a diuretic and in treatment of conditions related to the urinary system. As understanding of chemistry evolves, urea is recognized for its fertilizing properties, leading to widespread use in agriculture by the late 19th century.
Modern Uses of Urea
Fertilizer: It is one of the most common nitrogenous fertilizers, important for enhancing crop yields.
Industrial Chemicals: Urea is used in the production of resins, plastics, and adhesives. It is also utilized in the manufacture of melamine.
Medical Applications: Urea is included in some topical creams and ointments for its hydrating properties, especially in treating dry skin.
Animal Feed: It serves as a non-protein nitrogen source in ruminant nutrition, promoting protein synthesis in the animals' digestive systems.
Food Industry: It's used as a food additive in animal feed to provide essential nitrogen.
Cosmetics: Urea's moisturizing properties make it popular in skincare products, particularly creams and lotions, where it helps to hydrate and soften skin.
Relationship Between Urea and Sporosarcina pasteurii Bacterium
Sporosarcina pasteurii, a bacterium found in soil and water, has the unique capability to utilize urea as a nitrogen source. This bacterium converting urea into ammonia through the process of ureolysis. In engineering applications, S. pasteurii is used in biocementation.
This microorganism produces calcium carbonate (calcite, limestone, CaCO3) as a byproduct. This natural interaction is creatively applied in construction, with developments like self-healing concrete and bio-cement.
Facts About Urea
Urea is known as a "green" fertilizer as it reduces nitrogen leaching and can enhance soil health.
It is approximately 46% nitrogen by weight, making it one of the most concentrated nitrogen fertilizers available.
Urea was historically referred to as "urea nitrate" when it was formed with nitric acid for fertilizer applications.
The body regulates urea synthesis through the urea cycle, a key metabolic pathway in mammals.
It comprises about 2% of urine's total composition.
More than 100 million tons of fertilizer produced globally each year include urea.
Urea is the first organic compound synthesized from inorganic materials, marking a significant chemical achievement.
It's present in many foods like meat and dairy.
Synthetic urea is generally made from ammonia and carbon dioxide under high-pressure conditions.
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