The conversion of dinitrogen, present in the air, to ammonia is known as nitrogen fixation. Nitrogen is an essential component of the living system but molecular nitrogen can not be used by most living organisms except a few microorganisms. The reduction of molecular nitrogen to ammonia by living organisms is known as biological nitrogen fixation. Some prokaryotes have the ability to fix nitrogen, they are called nitrogen fixers.

1. What is the first stable product of nitrogen fixation in the root nodules of leguminous plants?

(a) Glutamate

(b) NO₃^–

(c) Ammonia

(d) NO₂^–

Answer: (c)

2. Which of the following is required for the action of the nitrogenase enzyme?

(a) Light

(b) High input of energy

(c) Super oxygen radicals

(d) Mn²⁺

Answer: (b)

3. Leghaemoglobin is present in the root nodules of legumes. What is the function of leghaemoglobin?

(a) Oxygen removal

(b) Inhibition of nitrogenase activity

(c) Expression of nif gene

(d) Nodule differentiation

Answer: (a)

4. An aquatic fern that performs nitrogen fixation is _______.

(a) Nostoc

(b) Azolla

(c) Salvinia

(d) Salvia

Answer: (b)

5. Which of the following is correct for nitrifying bacteria?

(a) They convert free nitrogen to nitrogen compounds

(b) They oxidize ammonia to nitrates

(c) They reduce nitrates to free nitrogen

(d) They convert proteins into ammonia

Answer: (b)

6. Which of the following prevents the inactivation of nitrogenase by oxygen?

(a) Cytochrome

(b) Carotene

(c) Xanthophyll

(d) Leghaemoglobin

Answer: (d)

7. Nitrogen is absorbed by plants as _____.

(a) Nitrites

(b) Ammonium

(c) Nitrites

(d) All of the above

Answer: (d)

8. Industrial nitrogen fixation is carried out by _____.

(a) Friedel Crafts reaction

(b) Helmonts process

(c) Haber process

(d) None of the above

Answer: (c)

9. This element plays a key role in the nitrogen fixation.

(a) Manganese

(b) Molybdenum

(c) Zinc

(d) Copper

Answer: (b)

10. Cells where nitrogen fixation takes place in Nostoc are known as _____.

(a) Hormogonia

(b) Heterocysts

(c) Akinetes

(d) Nodules

Answer: (b)

These were some MCQs on the Nitrogen Fixation. Learn MCQs on related topics for NEET, at BYJU’S.