Nitrogen fixation

Definition

Nitrogen fixation is the biological process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3) by certain prokaryotes. This process is essential for incorporating atmospheric nitrogen into organic compounds.

5 Must Know Facts For Your Next Test

1. Nitrogen-fixing bacteria, such as Rhizobium, form symbiotic relationships with leguminous plants.
2. The enzyme nitrogenase catalyzes the conversion of atmospheric nitrogen to ammonia.
3. Cyanobacteria are notable non-symbiotic nitrogen fixers found in various aquatic environments.
4. Nitrogen fixation requires a significant amount of ATP due to the triple bond in molecular nitrogen.
5. Fixed nitrogen is incorporated into amino acids, nucleotides, and other cellular components.

Review Questions

• Which enzyme is responsible for catalyzing the conversion of atmospheric nitrogen to ammonia?
• Name one type of bacteria that forms a symbiotic relationship with plants for nitrogen fixation.
• Why does nitrogen fixation require a substantial amount of energy?

Related terms

Symbiosis:

A close and often long-term interaction between two different biological species.

Nitrogenase: An enzyme complex that facilitates the reduction of atmospheric nitrogen to ammonia.

Cyanobacteria:

Photosynthetic bacteria that can also fix atmospheric nitrogen in aquatic ecosystems.