What is the term for the process of converting nitrogen gas into ammonia?

• A. Nitrogen fixation
• B. Endospore
• C. Eukaryote
• D. Prokaryote

Answer: (A)

Nitrogen fixation is the process of converting atmospheric nitrogen (N2) into ammonia (NH3). This reaction is carried out by certain bacteria and archaea that possess the enzyme nitrogenase, which uses ATP energy to break the very strong N≡N triple bond and reduce N2 to NH3. Ammonia then becomes available for incorporation into amino acids, nucleotides, and other biomolecules, fueling growth. In nature, this often occurs in symbiotic relationships within legume root nodules or by free-living soil microbes. Endospore is a survival structure some bacteria form under stress, not a nitrogen-converting reaction. Eukaryote and prokaryote describe cell types, not processes, so they don’t describe how nitrogen is chemically transformed.