What is the primary function of nitrogen fixation in biology?

The primary function of nitrogen fixation in biology is to convert nitrogen gas (N2) from the atmosphere into ammonia (NH3). This process is critical because most organisms cannot utilize atmospheric nitrogen directly. Nitrogen fixation allows for the incorporation of nitrogen into organic compounds, making it available for use by living organisms.

This conversion is facilitated by certain bacteria, including free-living bacteria and symbiotic bacteria that often associate with plant roots, particularly legumes. The ammonia produced through nitrogen fixation can then be used by plants to synthesize amino acids and nucleic acids, which are essential for growth and development. Without nitrogen fixation, the nitrogen cycle would be disrupted, leading to a deficiency in a necessary nutrient for all forms of life.

In contrast, the other functions listed are unrelated to the process of nitrogen fixation. Decomposing organic matter involves breaking down dead organisms and returning nutrients to the ecosystem but does not specifically relate to converting nitrogen gas. Producing energy for cells refers to cellular respiration and metabolic processes that generate ATP, while synthesizing proteins involves using amino acids—which can originate from fixed nitrogen—but does not encompass the fixation process itself.