The enzyme nitrogenase is inhibited by oxygen. Nitrogenase activity is protected by the following mechanism:
A) special thick-walled cells (heterocysts) in filamentous cyanobacteria, such as Anabaena
B) special nitrogenase-protecting proteins in Azotobacter species
C) temporal separation of nitrogen fixation (at night) and photosynthesis (during the day) in some species of cyanobacteria
D) all of the above
E) none of the above

Question

Quizplus · Accepted Answer

The mechanism of nitrogenase protection includes all the options mentioned in the answer choices. Heterocysts in Anabaena provide a microaerobic environment for nitrogenase activity, special nitrogenase-protecting proteins in Azotobacter species protect nitrogenase from oxygen, and some species of cyanobacteria separate nitrogen fixation and photosynthesis temporally to avoid oxygen production during nitrogen fixation. Therefore, option D is the correct answer.

The Enzyme Nitrogenase Is Inhibited by Oxygen