Cycles -Nitrogen cycle

Lightning fixes a relatively insignificant amount of elemental nitrogen. The electrical energy released from the discharge of electrical charge splits the stable triple bond of the nitrogen molecule.

N_2(g) + O_2(g) --> 2NO_(g)
2NO_(g) + O_2(g) -->2NO_2(g)

Broad beans, peas and clover are examples of a group of plants called legumes. These plants have a symbiotic relationship with bacteria known as Rhizobium. The bacteria invade the roots of these plants and form nodules. The bacteria proceed to fix atmospheric nitrogen through enzyme action to produce ammonia(NH₃) or ammonium ions(NH₄⁺).

Animals (herbivores) consume nitrogen from plants in the form of proteins. Nitrogen enters the food chain and is used to form DNA, proteins for control of cell function and for the synthesis of structural material.

Animals do not store the nitrogen compounds(amino acids) consumed and what ever is not needed is disposed of in the form of urea.

Plants use the nitrogen in the form of soluble nitrates and nitrites to produce organic material that eventually finds its way into the food chain.

Nitrogen cycle
Click on the blue writing for more information
Nitrogen forms of the gases of the atmosphere. Nitrogen from the atmosphere is converted to ammonium (NH₄⁺) compounds by Nitrogen (N₂ ) is converted to nitrous oxide (NO) by Denitrifying bacteria Click for a more detailed diagram.
The above diagram outlines the pathways atmospheric nitrogen is cycled through the biosphere. Nitrogen exists in animals mainly in the form of proteins. Amino acids are not stored and are broken down to form urea when not used to make protein. Occasionally, during starvation, protein is used as an energy source but only after the amine group from the amino acids are removed. The amino group is combined with carbon dioxide to form urea((NH₂)₂CO). Legumes provide a source of soluble nitrogen compounds able to be used by plants. Often legumes are planted in fields during winter to increase the nitrogen content of the soil without having to use artificial fertilizers. Exercises
Eutrophication

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