What defines micronutrients?

Micronutrients are essential vitamins and minerals that play a critical role in the body's biochemical processes. They are required in smaller quantities than macronutrients (such as carbohydrates, proteins, and fats), but they are vital for maintaining health and supporting various physiological functions.

The correct answer, which highlights their necessity for electro-chemical reactions, is particularly relevant because many micronutrients, such as minerals like potassium, calcium, and magnesium, are involved in processes like nerve transmission, muscle contraction, and hydration. These processes depend on electrochemical gradients that are maintained by these essential nutrients.

In contrast, the other options do not accurately describe the role of micronutrients. They are not primarily used for building muscle (which is more related to macronutrients like proteins), they do not occur in larger amounts (they are actually needed in minute quantities), and they do not serve as direct sources of energy since they do not provide calories like macronutrients do. Instead, they support various metabolic processes that help the body utilize energy from macronutrients effectively.