Ligand (primary messenger) Receptor CYTOSOL Receptor-ligand binding 3)Cellular responses NUCLEUS Signal transduction (via second messengers) (4)Changes in gene expression Figure 10-2 The Overall Flow of Information During Cell Signaling Binding of ligand by a receptor activates a series of events known as signal transduction, which relays the signal to the interior of the cell, resulting in specific cellular responses and/or changes in gene expression