Question

why are body did not need nitrogen

Answer 1

Nitrogen is not used by our body in its gaseous form. It does play a major role in the formation of proteins. Each amino acid (building block of protein) contains a special end group called an amino group (NH2). Without it it would not be an amino acid. Also Nitrogen is found in DNA and RNA. It is a major factor in the nitrogenous bases A,T,C,G,and U. Also it is found in our metabolic waste. Ammonia, urea, uric acid are metabolic wastes that are used as plant fertilizers. Certain bacteria have the ability to change atmospheric nitrogen into nitrates. They are found in a symbiotic relationship with certain plants called legumes. Nitrogen in that form (N2) cannot be utilized by living things. Only a few types of bacteria can convert nitrogen to ammonia, nitrites, and nitrates. This process is called nitrogen fixation. Ammonia, nitrites, and nitrates are taken up by plants and converted to amino acids. We get amino acids by eating plants (or eating animals that eat plants, or animals that eat animals that eat animals that eat plants, etc.)