Urea is the primary end product of nitrogen metabolism in humans. It's excreted from the body in urine. The nitrogen atom is one of the distinctive features of the amino acid, but it also represents a danger if it is not properly dispatched. Therefore, the synthesis and proper disposal of urea is vital to the health of the human body.
Function
Amino acids are the building blocks of proteins, the molecules that essentially carry out most of the body's important functions. Once assembled in the proper order by our genetic code, proteins facilitate chemical reactions, transport molecules like oxygen through the body, support the immune system, regulate the metabolism, contract the muscles and play roles as structural components in organs and tissue. There are 20 amino acids total, but about half of them cannot be synthesized and must be obtained through the diet. Missing one amino acid can create a serious deficiency in the body.
Features
Amino acids are bonded together in complex three-dimensional structures to form proteins. Each amino acid is distinctive, but they also share a number of things in common. For example, all amino acids contain a molecular group called an amine, which consists of a base nitrogen atom with a lone pair of electrons that don't bond to or share with other atoms. This gives the amino acids unique bonding abilities.
Deamination
Deamination is a type of reaction in which the amine group is removed from the amino acid and converted into a colorless gas known as ammonia that is hazardous to living organisms. This reaction occurs in the liver when amino acids need to be broken down from excess protein intake.
Significance
Because ammonia is toxic to the blood, it must be converted to urea in a process known as the urea cycle. The reaction first requires two ammonia molecules and a carbon dioxide molecule as the reactants. Two ATP, the primary unit of energy in the body, are used to drive the reaction forward. When it is finished, the reaction produces urea and water. The urea must then be transported from the liver to the kidneys for excretion from the body. Through the act of ammonia conversion, excess protein in the diet will create more urea for excretion.
Warning
Normally the body has minimal trouble clearing away nitrogen. However, liver or kidney problems may complicate its removal. There is no alternative pathway, so a block in any step in the urea cycle is fatal. Damage to the enzymes responsible for the chemical reactions may be inherited or result from liver cirrhosis and cause a partial block. If ammonia continues to accumulate in the body, then there will be further degradation of the kidneys. According to Dr. Mackenzie Walser of John Hopkins, a protein restriction appears to slow progression of chronic renal failure in experimental models and in patients.
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