How do G protein-coupled receptors (GPCRs) interact with the G protein to initiate cellular signaling pathways?

When a signaling molecule binds to a G protein-coupled receptor (GPCR) on the cell surface, it causes a change in the receptor's shape. This change allows the GPCR to interact with a G protein inside the cell. The G protein then becomes activated and triggers a series of events that ultimately lead to the initiation of cellular signaling pathways.