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. leghaemoglobin scavenges oxygen and is pinkish in colour
• B. nodules act as sites for nitrogen fixation
• C. the enzyme nitrogenase catalyses the conversion of atmospheric $N_2$ to $NH_3$
• D. nitrogenase is insensitive to oxygen

Answer 1

The Correct Option is D

1. The enzyme nitrogenase is sensitive to molecular oxygen. The enzyme requires anaerobic condition during nitrogen fixation, but live as aerobes under free-living conditions.
2. Leg-haemoglobin provides anaerobic condition to the enzyme nitrogenase. It protects the enzyme from oxygen. It scavenges oxygen and is pinkish in colour.
3. As nodules contain necessary biochemical components so that helps in fixing atmospheric nitrogen to ammonia. They act like sites of nitrogen fixation.
4. The enzyme nitrogenase catalyses the conversion of atmospheric nitrogen to ammonia. It requires 8 ATP. The energy obtained from the respiration of the host plant.

Answer 2

Ans: Symbiotic nitrogen fixation, is the biological process in which organisms such as baterias help in the conversion of atmospheric nitrogen into ammonia. The enzyme nitrogenase is involved in this process. It is essential for the infertility of the ecosystem. The bacteria that are involved in the symbiotic nitrogen fixation are present in the root nodules of the leguminous plants such as beans, clover.

The process of symbiotic nitrogen fixation is as follows:

• A compound is released by the leguminous plants that will help in the attraction of nitrogen fixing bacteria. 
• The bacteria will form a symbiotic relation with the plants. These bacteria are sensitive to oxygen therefore leghaemoglobin is present that will act as oxygen scavenger. 
• The infected root will form curls known as root nodules. The bacteria will convert the atmospheric nitrogen into ammonia, through nitrogen fixation. This form of nitrogen can be used by plants. 
• The ammonia will then get converted into ammonium ion and then incorporated into organic compounds like amino acids and proteins. 
• The plants in return will provide the bacteria with nutrients as the source of energy that is required for their metabolism.