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The urea cycle converts highly toxic ammonia to urea for excretion. [1] This cycle was the first metabolic cycle to be discovered by Hans Krebs and Kurt Henseleit in 1932, [2] [3] [4] five years before the discovery of the TCA cycle. The urea cycle was described in more detail later on by Ratner and Cohen.
The excretion of urea is called ureotelism. Land animals, mainly amphibians and mammals, convert ammonia into urea, a process which occurs in the liver and kidney. These animals are called ureotelic. [3] Urea is a less toxic compound than ammonia; two nitrogen atoms are eliminated through it and less water is needed for its excretion.
The Wöhler synthesis is the conversion of ammonium cyanate into urea. This chemical reaction was described in 1828 by Friedrich Wöhler. [1] It is often cited as the starting point of modern organic chemistry. Although the Wöhler reaction concerns the conversion of ammonium cyanate, this salt appears only as an
Ammonia is toxic to the human system, and enzymes convert it to urea or uric acid by addition of carbon dioxide molecules (which is not considered a deamination process) in the urea cycle, which also takes place in the liver. Urea and uric acid can safely diffuse into the blood and then be excreted in urine.
Urea plant using ammonium carbamate briquettes, Fixed Nitrogen Research Laboratory, ca. 1930 Carl Bosch, 1927. The Bosch–Meiser process is an industrial process, which was patented in 1922 [1] and named after its discoverers, the German chemists Carl Bosch and Wilhelm Meiser [2] for the large-scale manufacturing of urea, a valuable nitrogenous chemical.
Selective catalytic reduction (SCR) means converting nitrogen oxides, also referred to as NO x with the aid of a catalyst into diatomic nitrogen (N 2), and water (H 2 O). A reductant, typically anhydrous ammonia (NH 3), aqueous ammonia (NH 4 OH), or a urea (CO(NH 2) 2) solution, is added to a stream of flue or exhaust gas and is reacted onto a ...
By Gwladys Fouche and Tom Little. OSLO (Reuters) -A tram derailed and crashed into a store in central Oslo on Tuesday, injuring the driver and at least three other people, Norwegian police said.
A second type of transamination reaction can be described as a nucleophilic substitution of one amine or amide anion on an amine or ammonium salt. [1] For example, the attack of a primary amine by a primary amide anion can be used to prepare secondary amines: RNH 2 + R'NH − → RR'NH + NH 2 −