BIOL 205 Lecture 12: BIOL 205 Biology of Organisms lecture 12
Document Summary
Nitrogen fixation: nitrogen in nature exist in gaseous form, nitrogen gas molecules have triple bond, not easy to break the bond to harvest the energy, abiotic fixation. Lighting has enough energy to break down water and nitrogen molecules to make nitric acid. Dissolved in soil as nitrate ions and used by plants. Needs high pressure, temperature and catalyst: biotic fixation. Free living organisms/bacteria (e. g. blue green algae) Nitrogen fixation is sensitive to o2: o2 it toxic to enzyme nitrogenase and inactivates it, can be avoided by. Intense cell respiration use up all the o2. Photosynthesis during the day and n2 fixation at night, (separate by time) Fixation only occurs in cells that lack photosystem ii (separate by space) e. g. cyanobacteria/filament of anabaena, n2 fixation only takes place in heterocyst. Higher plants have root nodules with leghemoglobin, an enzyme that maintains equilibrium between immobilizing o2 and releasing enough o2 for respiration.
