Which substances are essential to life but required in very small amounts for body growth and activity?

Vitamins are indeed essential to life and the correct answer because they play crucial roles in various biochemical processes necessary for growth, development, and overall health. These organic compounds function as coenzymes or as precursors for coenzymes, which participate in metabolic pathways.

For example, certain vitamins are vital for energy production, immune function, and the maintenance of healthy skin, eyes, and blood. The body does not produce most vitamins in sufficient quantities, requiring them to be obtained from the diet. Although they are needed in small amounts, their absence can lead to significant health issues, underscoring their importance.

While minerals also fit the description of essential substances required in small amounts, vitamins are specifically tailored to the context of biological activity and growth. Fibers, on the other hand, are important for digestive health but are not classified directly as vitamins or minerals. Amino acids are vital for protein synthesis and contribute to various bodily functions but are generally required in larger amounts compared to vitamins.