What is the role of a signal transduction pathway?

A signal transduction pathway is crucial in cellular communication, as it transmits signals from the cell surface to target molecules inside the cell. This process begins when a signaling molecule, such as a hormone or neurotransmitter, binds to a receptor on the cell membrane. This binding initiates a cascade of biochemical reactions and interactions, often involving various proteins, enzymes, and secondary messengers. These intracellular events ultimately lead to changes in cellular activities, such as gene expression, enzyme activity, or cell growth and differentiation.

By enabling cells to respond appropriately to external signals, signal transduction pathways play a vital role in regulating many physiological processes, including metabolism, immune responses, and cell division. This function distinguishes it clearly from options that refer to nutrient transport, structural support, or oxygen transport, which pertain to different cellular mechanisms.