Biochemistry

Step 1: Understanding the Concept:
Biological nitrogen fixation is the process where atmospheric nitrogen ( ) is converted into ammonia ( ). This reaction is catalyzed by the nitrogenase enzyme complex and is extremely energy-intensive, requiring a significant amount of ATP.
Step 2: Key Formula or Approach:
The overall balanced chemical equation for biological nitrogen fixation is:
Step 3: Detailed Explanation:
As shown in the equation, the reduction of one molecule of dinitrogen ( ) to form two molecules of ammonia ( ) requires the hydrolysis of 16 molecules of ATP to ADP and inorganic phosphate ( ). This energy is used by the nitrogenase enzyme complex to overcome the high activation energy required to break the strong triple bond of the molecule. The process also requires 8 electrons and 8 protons. A byproduct, hydrogen gas ( ), is also formed.
Step 4: Final Answer:
To fix one molecule of , 16 molecules of ATP are consumed.

Step 1: Understanding the Concept:
The question asks to identify the key enzymes that are directly involved in the process of biological nitrogen fixation.
Step 2: Detailed Explanation:
The process of converting atmospheric nitrogen ( ) to ammonia ( ) involves a complex interplay of enzymes.
Nitrogenase: This is the primary and essential enzyme complex that catalyzes the reduction of to . It is highly sensitive to oxygen. No nitrogen fixation can occur without it.
Hydrogenase: A significant side reaction of the nitrogenase enzyme is the production of hydrogen gas ( ), which wastes energy (ATP) and reducing power (electrons). Many nitrogen-fixing organisms possess an "uptake hydrogenase" enzyme. This enzyme recaptures the and oxidizes it, thereby recovering some of the energy that was lost. Therefore, hydrogenase is a very important enzyme for improving the overall efficiency of nitrogen fixation.
Peptidase, Hexokinase, Dehydrogenase: These are important enzymes in general cellular metabolism (protein breakdown, glycolysis, respiration) but are not the specific key enzymes of the nitrogen fixation pathway itself.
Step 3: Final Answer:
Both Nitrogenase (for the main reaction) and Hydrogenase (for improving efficiency) are the important enzymes involved in nitrogen fixation.