Assess graduate-level understanding of mechanistic principles of G protein–coupled receptor (GPCR) signaling, including molecular determinants of ligand recognition and selectivity, receptor conformational changes that drive heterotrimeric G protein engagement and GDP→GTP exchange, GTP hydrolysis and inactivation, and coupling to downstream effectors (adenylyl cyclase, phospholipase C, ion channels) and regulatory partners (arrestins, RGS). Items may ask for interpretation of structural/biophysical data and prediction of signaling outcomes from specific perturbations.