Question

Leguminous plants are able to fix atmospheric nitrogen through the process of symbiotic nitrogen fixation. Which one of the following statements is not correct during this process of nitrogen fixation?

• A. Nodules act as sites for nitrogen fixation
• B. The enzyme nitrogenase catalyzes the conversion of atmospheric N₂ to NH₃
• C. Leghaemoglobin scavenges oxygen and is pinkish in color
• D. Nitrogenase is insensitive to oxygen

Answer 1

The correct option is D

Nitrogenase is insensitive to oxygen

The correct option is D:

Explanation of the correct option:

1. In a mutualistic relationship known as symbiotic nitrogen fixation, plants give bacteria a habitat and fixed carbon in exchange for fixed nitrogen.
2. The essential enzyme for biological nitrogen-fixing is nitrogenase.
3. The process of nitrogen fixation involves turning atmospheric nitrogen (N₂) into ammonium (NH₄⁺), nitrates (NO₃^-), or nitrites (NO₂^-).
4. Natural or manmade nitrogen-fixing is also possible.
5. Nitrogen is converted into ammonia by nitrogenase.
6. It exists in a few prokaryotes.
7. The main enzyme in charge of fixing nitrogen is nitrogenase.
8. But because of its sensitivity to oxygen, this enzyme's activity is permanently suppressed by oxygen.
9. Some bacteria are claimed to possess nitrogenases that can continue to fix N₂ in the presence of O₂.

Explanation of the incorrect option:

Option A:

1. This is due to the fact that leguminous plants' root nodules contain essential biochemical elements.
2. These elements aid in the conversion of atmospheric nitrogen to inorganic ammonia.
3. Leguminous plants' roots frequently contain root nodules.
4. They develop as a result of their connection to the nitrogen-fixing bacterium Rhizobium.

Option B:

1. The enzyme nitrogenase catalyzes the transformation of atmospheric N₂ to NH₃, which is the second claim made.
2. This statement is true.
3. The essential enzyme for biological nitrogen-fixing is nitrogenase.
4. Because nitrogenase catalyzes the transformation of atmospheric nitrogen into inorganic ammonia, this is the case.

Option C:

1. The leghemoglobin is pinkish in hue and scavenges oxygen, according to the second assertion made.
2. This assertion is true.
3. This is so that the nitrogenase enzyme can function in an anaerobic environment or under anaerobic conditions provided by the leg-hemoglobin.
4. Leg-hemoglobin also scavenges oxygen to shield the nitrogenase enzyme from it.
5. Leg hemoglobin has a pinkish color.

Final answer: Nitrogenase is insensitive to oxygen and is not correct during this process of nitrogen fixation.