Which of the following is NOT a primary function of carbohydrates?

Carbohydrates primarily serve as an energy source and play crucial roles in structural components of cells. They are fundamental for energy storage, as seen in polysaccharides like glycogen and starch. Additionally, carbohydrates contribute to structural integrity in organisms, particularly in plants with cellulose and in the exoskeletons of certain arthropods.

While carbohydrates can participate in cellular communication, such as through glycoproteins and glycolipids on cell surfaces, they do not function as hormones. Hormones are typically proteins or steroids that facilitate communication and regulatory processes within the body. Thus, serving as hormones is not a primary role of carbohydrates, making that the correct choice in this context.