Correct Option
Potassium (K), Sodium (Na), Magnesium (Mg), and Calcium (Ca) are among the essential elements required by living organisms in major quantities. These are classified as macronutrients due to their high demand for various physiological and biochemical processes:
- Potassium (K): Crucial for maintaining osmotic balance, regulating stomatal movement in plants, and acting as a cofactor for numerous enzymes.
- Sodium (Na): Essential for nerve impulse transmission, muscle contraction, and maintaining fluid balance in animals.
- Magnesium (Mg): A central atom in the chlorophyll molecule, vital for photosynthesis. It also serves as a cofactor for enzymes involved in ATP synthesis and nucleic acid metabolism.
- Calcium (Ca): Important for cell wall structure in plants, bone and teeth formation in animals, blood clotting, and muscle function.
These elements are required in substantial amounts compared to micronutrients.
Incorrect Options
Options (1), (2), and (4) include a mix of macronutrients and micronutrients. While potassium, sodium, magnesium, and calcium are macronutrients, elements like manganese (Mn), molybdenum (Mo), and copper (Cu) are micronutrients or trace elements. Living organisms require these micronutrients in very small quantities for specific enzymatic activities or structural roles, not in major quantities.
- Option (1): Potassium and calcium are macronutrients, but manganese and molybdenum are micronutrients.
- Option (2): Potassium and calcium are macronutrients, but molybdenum and copper are micronutrients.
- Option (4): Sodium and magnesium are macronutrients, but copper and manganese are micronutrients.