The steps of the Nitrogen Cycle
Nitrogen gas in converted into ammonium and then it is converted to nitrites and then nitrates which are assimilated plants, to make their proteins. Plants that get nitrogen this way can't make as much protein as plants in the legume family. This is why they are not a goof source of protein.
Why is this important to living things?
The nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. Nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and DNA, the building blocks of all life.
How do living things disrupt the cycle?
One of the major influences of humans on the nitrogen cycle occurs through the use of nitrogen-containing fertilizers in agriculture. Under conditions in which agricultural plants have access to as much water as they require, their productivity is usually constrained by the rate at which they can obtain nitrogen in available forms, particularly nitrate, and sometimes ammonium. Humans also influence the nitrogen cycle by dumping sewage and other types of organic matter into water-bodies