BRAINCAKENitrogen-Fixing Bacteria
Nitrogen fixation is the conversion of nitrogen gas (N2) into ammonia (NH3), which dissolves in soil water to form ammonium ions (NH4+). Only certain prokaryotes can do this biologically.
The reaction is catalysed by the enzyme nitrogenase, which reduces N2 to ammonia. It needs a lot of ATP and hydrogen, and nitrogenase is inactivated by oxygen, so it must work in anaerobic conditions.
Mutualistic nitrogen-fixing bacteria
Rhizobium lives inside swellings called root nodules on the roots of leguminous plants (legumes), such as peas, beans and clover. The relationship is mutualistic:
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More in Ecosystems
- Calculating Efficiency of Biomass Transfer
- Human Activities and Biomass Transfer
- Decomposers
- The Nitrogen Cycle
- Nitrification and Denitrification
- The Carbon Cycle
- Succession
- Primary Succession
All 21 lessons in Ecosystems · All OCR A-level Biology topics