Nitrogen fixation

Definition

Nitrogen fixation is the process by which molecular nitrogen ($N_2$) in the atmosphere is converted into ammonia ($NH_3$) or related nitrogenous compounds in soil. This process is essential for making nitrogen available to living organisms.

5 Must Know Facts For Your Next Test

1. Nitrogen fixation can occur abiotically through industrial processes like the Haber-Bosch process, or biologically via microorganisms such as Rhizobium bacteria.
2. Biological nitrogen fixation typically involves the enzyme nitrogenase, which catalyzes the conversion of $N_2$ to ammonia ($NH_3$).
3. Plants cannot directly use atmospheric $N_2$, so nitrogen fixation is crucial for converting it into forms they can assimilate, such as nitrates and ammonium ions.
4. Leguminous plants have symbiotic relationships with nitrogen-fixing bacteria in root nodules, facilitating nutrient uptake.
5. Fixed nitrogen compounds are vital components of amino acids, nucleic acids, and chlorophyll.

Review Questions

• What role does the enzyme nitrogenase play in biological nitrogen fixation?
• How do leguminous plants benefit from their relationship with Rhizobium bacteria?
• Explain why nitrogen fixation is essential for plant growth.

Related terms

Haber-Bosch Process:

An industrial method for synthesizing ammonia from atmospheric nitrogen and hydrogen gas under high pressure and temperature using a metal catalyst.

Rhizobium:

A genus of bacteria that form symbiotic relationships with legumes to fix atmospheric nitrogen into a form usable by plants.

$NH_3$ (Ammonia): A compound of nitrogen and hydrogen that serves as a key product of both biological and industrial nitrogen fixation processes.