Ammonia nitrogen cycle

A class of enzymes found in bacteria within root nodules in some plants, which catalyze reactions by which N2 molecules from the air are converted to ammonia. Nitrogen Cycle... 

There is also considerable current environmental interest in hyponitrite oxidation because it is implicated in the oxidation of ammonia to nitrite, an important step in the nitrogen cycle (p. 410). Specifically, it seems likely that the oxidation proceeds from ammonia through hydroxylamine and hyponitrous acid to nitrite (or N2O). 

The global nitrogen cycle is often referred to as the nitrogen cycles, since we can view the overall process as the result of the interactions of various biological and abiotic processes. Each of these processes, to a first approximation, can be considered as a self-contained cycle. We have already considered the biological cycle from this perspective (Fig. 12-1), and now we will look at the other processes, the ammonia cycle, the cycle, and the fixation/denitrification cycle. 

The urea cycle is essential for the detoxification of ammonia 678 Urea cycle defects cause a variety of clinical syndromes, including a metabolic crisis in the newborn infant 679 Urea cycle defects sometimes result from the congenital absence of a transporter for an enzyme or amino acid involved in the urea cycle 680 Successful management of urea cycle defects involves a low-protein diet to minimize ammonia production as well as medications that enable the excretion of ammonia nitrogen in forms other than urea 680... 

Because the reaction is an equilibrium process, with a typical yield of 15% ammonia per cycle, the gases leaving the converter are cooled whilst still under pressure. The ammonia is liquefied and removed, whilst the unreacted nitrogen and hydrogen are recycled to the converter. 

Many fertilizers are based on ammonia compounds. Modem agriculture requires more nitrogen in soils than is normally replaced by the nitrogen cycle, hghtning, decaying plants and animals, and other natural means... 

Studies on nitrogen cycle enzymology in microorganisms that use ammonia as a major source of energy for growth suggest that HA serves as an intermediate in its oxidation to nitrite , as depicted in equations 1 and 2 ... 

The nitrogen cycle entails formation of ammonia by bacterial fixation of N2, nitrification of ammonia to nitrate by soil organisms, conversion of nitrate to ammonia by higher plants, synthesis of amino acids from ammonia by all organisms, and conversion of nitrate to N2 by denitrifying soil bacteria. 

One of the enzymes given in Table 23 is nitrogenase, which is responsible for the fixation of dinitrogen to give ammonia. Molybdenum probably serves as the binding site for N2, and is present in the iron-molybdenum cofactor, which is a molybdenum-iron sulfide cluster. Nitrogenase will be considered in Section 63.1.14, which deals with the nitrogen cycle. 

The nitrogen cycle is closely connected with the fluxes of hydrogen, sulfur, and other chemicals (Smith et al., 1998 Dimitroulopoulou and Marsh, 1997 Chapin et al., 2002 Rhee et al., 2005 Stevenson and Cole, 1999). Nitrogen and hydrogen react under great pressure and temperature in the presence of a catalyst to make ammonia. The study of correlations between the cycles of these elements is necessary to improve... 

The nitrogen cycle is the movement of nitrogen through the food chain from simple inorganic compounds, mainly ammonia, to complex organic compounds. 

Ammonia is found in the environment as the result of natural and industrial processes. It is released into the environment by the breakdown of organic wastes, and it is a constituent of the soil, the atmosphere, and bodies of water. Ammonia is also a key intermediate in the nitrogen cycle and is a product of amino acid metabolism (WHO 1986). Anhydrous ammonia is used in the production of nitric acid, explosives, synthetic fibers, and fertilizers (Budavari 1989). It is used as a refrigerant as a corrosion inhibitor in the purification of water supplies in steel production as a catalyst for polymers as a preservative for latex and in the production of nitrocellulose, urea formaldehyde, sulfite cooking liquors, and nitroparaffins (ACGIH 1991 Lewis 1993). Ammonium hydroxide (10-35% ammonia) is a major constituent of many cleaning solutions. Ammonia... 

Remember that in the natural nitrogen cycle (see Section 7.4.5), bacteria convert nutrient forms of nitrogen (i.e., ammonia and nitrite) back to nonnutritive N2 in the atmosphere. This process is called denitrification. For the biological removal of nitrogen, the activated sludge system is partitioned into zones, and the environment in each zone is... 

The nitrogen cycle. To be used by plants and animals, nitrogen must be converted from N2 to nitrogen-containing compounds, such as nitrates, ammonia, and proteins. The nitrogen is returned to the atmosphere by natural decay processes. 

Nitric oxide (NO), nitrous oxide (N2O), dinitrogen (N2), and ammonia (NH3) are constituents of the Earth s atmosphere. They play important roles in the chemistry and climate of the present-day Earth. Moreover, they are intermediates of the oceanic nitrogen cycle. In contrast to most of the other components of the oceanic nitrogen cycle, they exist as dissolved gaseous molecules. Being gases they can be transferred across the seasurface-troposphere interface. 

McCaig, A. E., Phillips, C. J., Stephen, J. R., Kowalchuk, G. A., Harvey, S. M., Herbert, R. A., Embley, T. M., and Prosser, J. I. (1999). Nitrogen cycling and community strucmre of proteo-bacterial P-subgroup ammonia-oxidizing bacteria within polluted marine fish farm sediments. Applied and Environmental Microbiology 213, 213-220. 

Nicol, G. W., and Schleper, C. (2006). Ammonia-oxidising Crenarchaeota Important players in the nitrogen cycle Trends Microbiol. 14, 207—212. 

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