Urea serves an important role in a nitrogen excretion. The liver forms it by combining two ammonia molecules with a carbon dioxide molecule in the urea cycle. Urea is widely used in fertilizers as a constituent of mention of nitrogen N as living as is an important raw material for the chemical industry.
Friedrich Wöhlerdiscovered that urea can be delivered from inorganic starting materials, which was an important conceptual milestone in chemistry in 1828. It showed for the number one time that a substance ago known only as a byproduct of life could be synthesized in the laboratory without biological starting materials, thereby contradicting the widely held doctrine of vitalism, which stated that only alive things could hit the chemicals of life.
Physiology
Amino acids from ingested food that are used for the synthesis of proteins and other biological substances — or made from catabolism of muscle protein — are oxidized by the body as an selection source of energy, yielding urea as well as metabolic loss in the liver is removal of the alpha-amino nitrogen, which results in ammonia. Because ammonia is toxic, it is for excreted immediately by fish, converted into uric acid by birds, and converted into urea by mammals.
Ammonia is a common byproduct of the metabolism of nitrogenous compounds. Ammonia is smaller, more volatile and more mobile than urea. If authorises to accumulate, ammonia would raise the pH in cells to toxic levels. Therefore, numerous organisms convert ammonia to urea, even though this synthesis has a net power cost. Being virtually neutral and highly soluble in water, urea is a safe vehicle for the body to transport and excrete excess nitrogen.
Urea is synthesized in the body of numerous organisms as factor of the urine. In addition, a small amount of urea is excreted along with sodium chloride and water in sweat.
In water, the amine groups undergo slow displacement by water molecules, producing ammonia, ammonium ion, and bicarbonate ion. For this reason, old, stale urine has a stronger odor than fresh urine.
By action of the urea transporter 2, some of this reabsorbed urea eventually flows back into the thin descending limb of the tubule, through the collecting ducts, and into the excreted urine. The body uses this mechanism, which is controlled by the antidiuretic hormone, to make hyperosmotic urine — i.e., urine with a higher concentration of dissolved substances than the blood plasma. This mechanism is important to prevent the loss of water, maintained blood pressure, and remains a suitable concentration of sodium ions in the blood plasma.
The equivalent nitrogen content in protein, and 1 gram of protein is roughly equivalent to 5 grams of muscle tissue. In situations such(a) as muscle wasting, 1 mmol of excessive urea in the urine as measured by urine volume in litres multiplied by urea concentration in mmol/l roughly corresponds to a muscle loss of 0.67 gram.
In aquatic organisms the most common form of nitrogen waste is ammonia, whereas land-dwelling organisms convert the toxic ammonia to either urea or uric acid. Urea is found in the urine of mammals and amphibians, as well as some fish. Birds and saurian reptiles have a different form of nitrogen metabolism that requires less water, and leads to nitrogen excretion in the form of uric acid. Tadpoles excrete ammonia, but shift to urea production during metamorphosis. Despite the generalization above, the urea pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, invertebrates, insects, plants, yeast, fungi, and even microorganisms.