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  2. Urea cycle - Wikipedia

    en.wikipedia.org/wiki/Urea_cycle

    The conversion from ammonia to urea happens in five main steps. The first is needed for ammonia to enter the cycle and the following four are all a part of the cycle itself. To enter the cycle, ammonia is converted to carbamoyl phosphate. The urea cycle consists of four enzymatic reactions: one mitochondrial and three cytosolic.

  3. Deamination - Wikipedia

    en.wikipedia.org/wiki/Deamination

    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.

  4. Metabolic waste - Wikipedia

    en.wikipedia.org/wiki/Metabolic_waste

    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.

  5. Wöhler synthesis - Wikipedia

    en.wikipedia.org/wiki/Wöhler_synthesis

    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

  6. Urea - Wikipedia

    en.wikipedia.org/wiki/Urea

    The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.

  7. Purine nucleotide cycle - Wikipedia

    en.wikipedia.org/wiki/Purine_nucleotide_cycle

    Ammonia (NH 3) diffuses into the blood, circulating to the liver to be neutralized by the urea cycle. (N.b. urea is not the same as uric acid, though both are end products of the purine nucleotide cycle, from ammonia and nucleotides respectively.)

  8. Transaminase - Wikipedia

    en.wikipedia.org/wiki/Transaminase

    Animals must metabolize proteins to amino acids, at the expense of muscle tissue, when blood sugar is low. The preference of liver transaminases for oxaloacetate or alpha-ketoglutarate plays a key role in funneling nitrogen from amino acid metabolism to aspartate and glutamate for conversion to urea for excretion of nitrogen.

  9. Cahill cycle - Wikipedia

    en.wikipedia.org/wiki/Cahill_cycle

    The Cahill cycle is less productive than the Cori cycle, which uses lactate, since a byproduct of energy production from alanine is production of urea. [5] Removal of the urea is energy-dependent, requiring four "high-energy" phosphate bonds (3 ATP hydrolyzed to 2 ADP and one AMP), thus the net ATP produced is less than that found in the Cori ...