Enzyme that fixes N2 in Plants



The enzyme that fixes N2 in plants is called nitrogenase. This enzyme is found in the root nodules of leguminous plants.

Evolution of H2 and Electrons and Protons



Nitrogenase catalyzes the reaction between N2 and H2 to produce ammonia (NH3) and hydrogen (H2). In this process, nitrogenase evolves H2 gas and transfers electrons and protons.

Number of Electrons and Protons



The number of electrons and protons associated with the evolution of H2 by nitrogenase is four electrons and four protons.

During the reaction, nitrogenase transfers a total of six electrons to N2 to reduce it to NH3. Of these, four electrons are transferred to H+ ions to produce H2 gas, and the remaining two electrons are used to reduce N2 to NH3.

The transfer of four protons is required to maintain the electro-neutrality of the reaction. The protons come from the surrounding medium, which is usually water or the cytoplasm of the cell.

Conclusion



In summary, the enzyme nitrogenase fixes N2 in plants by evolving H2 gas. The number of electrons and protons associated with this reaction is four electrons and four protons, respectively. The transfer of these electrons and protons is essential for the reduction of N2 to NH3 and the maintenance of electro-neutrality in the reaction.