Answer: Component of some amino acids (cysteine, methionine) and proteins.
- A Cross-links pectin polymers within the cell wall structure
- B Component of some amino acids (cysteine, methionine) and proteins
- C Regulates guard cell turgor pressure to control stomatal opening
- D Fixes atmospheric nitrogen gas into ammonia within root nodules
Correct answer: B. Component of some amino acids (cysteine, methionine) and proteins
Explanation: Sulfur is a component of amino acids cysteine and methionine, and thus of many proteins. It is also part of coenzymes (CoA) and vitamins. Deficiency causes chlorosis in young leaves (similar to N deficiency).
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.