What is nitrogen fixation?

Nitrogen fixation is the biological process by which atmospheric nitrogen gas (N₂), which is unavailable for direct use by most organisms, is converted into ammonia (NH₃) or related compounds in the soil. This process is essential because nitrogen is a crucial component of amino acids, proteins, and nucleic acids, and most living organisms cannot utilize atmospheric nitrogen directly for their metabolic processes.

Certain bacteria, including free-living species and symbiotic species that form relationships with plants (like legumes), have the necessary enzymes to carry out this conversion. By fixing nitrogen, these organisms play an essential role in the nitrogen cycle, making nitrogen accessible for other organisms, particularly plants, which can then incorporate it into organic compounds.

The other options do not correctly describe nitrogen fixation. The conversion of glucose into energy pertains to cellular respiration, the breakdown of organic matter involves decomposition processes, and nutrient absorption by plants refers to the uptake of essential minerals and compounds from the soil rather than the transformation of atmospheric nitrogen. Understanding nitrogen fixation underscores its importance in agriculture and ecology, as it contributes to soil fertility and plant growth.