Nitrogen metabolism refers to the processes by which living organisms convert nitrogen from various sources into usable forms. This includes the conversion of atmospheric nitrogen gas (N2) into ammonia (NH3) through a process called nitrogen fixation, primarily carried out by certain bacteria. Ammonia can then be transformed into other nitrogen compounds, such as nitrates (NO3-), which are essential for plant growth. In animals, nitrogen metabolism involves the breakdown of proteins and nucleic acids, leading to the production of urea and other nitrogenous waste products. These wastes are excreted through urine, helping to maintain nitrogen balance in the body. Overall, nitrogen metabolism is crucial for the synthesis of amino acids and nucleotides, which are vital for life.