What role do signaling molecules play in cells?

Signaling molecules play a crucial role in facilitating communication between cells. They are essential for various processes such as growth, immunity, and homeostasis. These molecules can be hormones, neurotransmitters, or other types of signaling proteins that transmit information from one cell to another. For example, when a signaling molecule binds to a receptor on a target cell, it triggers a response that can alter the target cell's behavior, such as initiating a metabolic process, changing gene expression, or activating a specific pathway.

This communication is vital for coordinating actions within an organism, allowing cells to respond to changes in their environment or to signals from other cells. In contrast, the other choices do not accurately represent the primary function of signaling molecules. Storing energy is more commonly the role of molecules like carbohydrates and lipids. Providing structural support is typically the function of proteins in the cytoskeleton or polysaccharides in the extracellular matrix. Nutrient absorption involves a different set of processes and molecules associated with the cell membrane and digestive systems. Thus, the primary and defining function of signaling molecules is indeed communication.