Biological nitrogen fixation

Definition

Biological nitrogen fixation is the process by which certain prokaryotes convert atmospheric nitrogen (N₂) into ammonia (NH₃), making it available for use by plants. This process is crucial for the nitrogen cycle and supports plant growth in ecosystems.

5 Must Know Facts For Your Next Test

1. Biological nitrogen fixation is primarily carried out by symbiotic bacteria such as Rhizobium, which form mutualistic relationships with leguminous plants.
2. Free-living bacteria like Azotobacter and Cyanobacteria also perform nitrogen fixation without a host plant.
3. The enzyme nitrogenase plays a critical role in the conversion of atmospheric nitrogen to ammonia during biological nitrogen fixation.
4. Nitrogen fixation is energy-intensive, requiring ATP and reducing power from electrons to drive the reduction of N₂ to NH₃.
5. Biological nitrogen fixation significantly contributes to soil fertility, reducing the need for chemical fertilizers in agriculture.

Review Questions

Related terms

Nitrogenase: An enzyme that facilitates the conversion of atmospheric nitrogen (N₂) to ammonia (NH₃).

Symbiosis:

A mutually beneficial relationship between different organisms, such as Rhizobium bacteria and leguminous plants.

Cyanobacteria:

A group of photosynthetic bacteria capable of both photosynthesis and biological nitrogen fixation.