1. What is nitrogen fixation?
A. Conversion of nitrogen gas into ammonia
B. Conversion of ammonia into nitrates
C. Conversion of nitrates into nitrogen gas
D. Conversion of ammonia into proteins
Answer: A
2. Which enzyme is primarily responsible for nitrogen fixation?
A. Rubisco
B. Nitrogenase
C. Amylase
D. Protease
Answer: B
3. Nitrogen fixation is mostly carried out by:
A. Animals
B. Plants
C. Bacteria
D. Fungi
Answer: C
4. Which of the following bacteria is involved in symbiotic nitrogen fixation?
A. Rhizobium
B. Azotobacter
C. Nitrosomonas
D. Nitrobacter
Answer: A
5. What is the primary energy source for nitrogen fixation in plants?
A. Glucose
B. ATP
C. NADPH
D. Oxygen
Answer: B
6. Nitrogenase is inactivated by:
A. Carbon dioxide
B. Oxygen
C. Water
D. Nitrogen gas
Answer: B
7. The process of nitrogen fixation occurs in:
A. Chloroplasts
B. Mitochondria
C. Root nodules
D. Cytoplasm
Answer: C
8. Which plant family predominantly forms symbiotic nitrogen-fixing associations?
A. Solanaceae
B. Poaceae
C. Fabaceae
D. Asteraceae
Answer: C
9. What is the role of leghemoglobin in nitrogen fixation?
A. Transporting ATP
B. Supplying nitrogen gas
C. Protecting nitrogenase from oxygen
D. Catalyzing nitrogen fixation
Answer: C
10. Which symbiotic association is involved in nitrogen fixation in non-leguminous plants?
A. Rhizobium and legumes
B. Azolla and cyanobacteria
C. Mycorrhizae and roots
D. Lichens and algae
Answer: B
11. What is the chemical formula for ammonia?
A. NH3
B. NO3
C. NH4+
D. NO2
Answer: A
12. Non-symbiotic nitrogen fixation is carried out by:
A. Mycorrhizae
B. Azotobacter
C. Rhizobium
D. Fungi
Answer: B
13. What is the role of ATP in nitrogen fixation?
A. Structural component of enzymes
B. Energy source for nitrogenase activity
C. Reducing agent for nitrogen gas
D. Electron donor in respiration
Answer: B
14. Which gas is reduced during nitrogen fixation?
A. Oxygen
B. Nitrogen
C. Carbon dioxide
D. Hydrogen
Answer: B
15. Which element is an essential cofactor for nitrogenase?
A. Magnesium
B. Molybdenum
C. Calcium
D. Sodium
Answer: B
16. Free-living nitrogen-fixing bacteria include:
A. Nitrosomonas
B. Azotobacter
C. Rhizobium
D. Pseudomonas
Answer: B
17. Cyanobacteria involved in nitrogen fixation are also called:
A. Blue-green algae
B. Diatoms
C. Protozoa
D. Brown algae
Answer: A
18. Which of the following is a leguminous plant?
A. Wheat
B. Pea
C. Rice
D. Maize
Answer: B
19. Biological nitrogen fixation requires:
A. Oxygen-rich conditions
B. Anaerobic conditions
C. High temperature
D. High salt concentration
Answer: B
20. Which crop benefits significantly from Rhizobium inoculation?
A. Maize
B. Cotton
C. Soybean
D. Sugarcane
Answer: C
21. What is the primary product of nitrogen fixation?
A. Nitrate
B. Ammonia
C. Nitrite
D. Proteins
Answer: B
22. The nodulation process in legumes begins with:
A. Root hair curling
B. ATP synthesis
C. Leaf formation
D. Photosynthesis
Answer: A
23. Which plant is associated with Frankia for nitrogen fixation?
A. Wheat
B. Alnus
C. Pea
D. Tomato
Answer: B
24. The Haber-Bosch process mimics:
A. Nitrogen fixation
B. Denitrification
C. Nitrification
D. Ammonification
Answer: A
25. Denitrification converts nitrogen compounds into:
A. Ammonia
B. Nitrates
C. Nitrogen gas
D. Proteins
Answer: C
26. Nitrogen fixation is a part of the:
A. Phosphorus cycle
B. Water cycle
C. Nitrogen cycle
D. Carbon cycle
Answer: C
27. Which gene cluster is essential for nitrogen fixation?
A. Nod genes
B. Nit genes
C. Nif genes
D. Fix genes
Answer: C
28. Rhizobia infect roots through:
A. Leaves
B. Root hairs
C. Stems
D. Flowers
Answer: B
29. Nitrogen-fixing bacteria convert atmospheric nitrogen into:
A. Proteins
B. Nitrates
C. Ammonia
D. Nitrites
Answer: C
30. Excess nitrogen in soil can lead to:
A. Reduced plant growth
B. Water pollution
C. Decreased photosynthesis
D. Enhanced respiration
Answer: B
