Answer: Essential cofactor for nitrogenase (N2 fixation) and nitrate reductase (NO3- to NO2-).
- A A central structural component found within the chlorophyll molecule itself according to conventional understanding
- B Essential cofactor for nitrogenase (N2 fixation) and nitrate reductase (NO3- to NO2-)
- C Required mainly for cross-linking pectin polymers during cell wall formation in routine practice
- D Required as a cofactor specifically in the light reactions of photosynthesis overall
Correct answer: B. Essential cofactor for nitrogenase (N2 fixation) and nitrate reductase (NO3- to NO2-)
Explanation: Molybdenum (Mo) is a micronutrient needed in the smallest amount of all essential elements. It is a cofactor for nitrogenase and nitrate reductase. Deficiency causes nitrogen deficiency symptoms even with adequate N supply ('whiptail' in cauliflower).
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.