What defines a vitamin's role as a coenzyme?

A vitamin's role as a coenzyme is defined by its ability to enhance metabolic pathways. Coenzymes are organic molecules, often derived from vitamins, that assist enzymes in catalyzing chemical reactions within the body. By participating in these biochemical pathways, coenzymes help facilitate processes such as metabolism, energy production, and the synthesis of molecules.

For example, B vitamins, such as niacin and riboflavin, function as coenzymes in critical reactions that convert macronutrients into usable energy. This highlights the vital role vitamins play in supporting metabolic activities, thereby making them essential for overall health and functioning.

The other options do not accurately reflect the specific role of vitamins as coenzymes. While some might enhance metabolic pathways, vitamins do not replace minerals, provide energy directly, or act independently; they typically work in conjunction with enzymes to ensure that metabolic processes run efficiently and effectively.