Nitrogen Cycle Assignment

Jake Garrison

Nitrogen Cycle Assignment

The first step in this process is nitrogen being released from the amino acid. This process is known as Ammonification. Alanine is used as an organic source because it is found in humus, which is dead organic matter. The Alanine is decomposed into simpler compounds by saprophytic bacteria and different fungi that live in the soil. They include the nitrogen from amino acids and proteins and release the excess nitrogen in the form of ammonium ions. The next part of this cycle is the oxidation of ammonium, also called nitrification. This step takes the nitrogen compound, in this case ammonia, and oxidizes it into nitrite and nitrate. This is a two step process. First the ammonium is oxidized into nitrite and then the nitrite is oxidized into nitrate. Nitrite is toxic, therefore, nitrate is the form that almost all nitrogen is absorbed by most crop plants grown on dry land; 2NH4 (ammonium) + 3O2 (Oxygen) Ñ-2NO-2(Nitrite) + 4H+ (hydrogen) + 2H2O. The next step is when 2NO-2 (Nitrite) + O2 (oxygen) Ñ- 2NO-3 (nitrate). This process is important because the plant must reduce it back to amino group (ammonium) before it can incorporate it into amino acids, and this costs energy. It would be better if the plant could skip this step, however, bacteria also want ammonium and due to the fact that there are more bacteria the plant will not get enough ammonium through direct absorption of ammonium. The next step is nitrogen reduction. This process reduces nitrate back into the amino group (ammonium). This allows the plant to absorb the ammonium ions. This is also a two step process. The first step takes place in the cytosol called nitrate reductase. This reduces nitrate to nitrite. The nitrate reductase enzyme contains FAD, Mo, and cytochrome 557, with a ferredoxin Fe4S4 center. Mo is bound to a cofactor containing a pteridine ring to form molybdopterin. The second step takes place in the plastids of plants. It is the process that takes nitrite and reduces it to ammonium. It produces a nitric oxide using FAD as a cofactor; it produces ammonia with heme and calcium as cofactors. After the Nitrate is reduced back to ammonium nitrogen, assimilation occurs. Assimilation is the addition of ammonium