After GDP is exchanged for GTP in GPCR activation, which sequence occurs?

Prepare for the Foundations of Biology Exam 1. Dive into key biological concepts with multiple choice questions, hints, and explanations. Ace the exam with our efficient study methods!

When the GDP on the alpha subunit is swapped for GTP, the active alpha subunit no longer stays bound to the beta-gamma dimer. It separates and travels to touch an effector protein, like adenylate cyclase, to turn on the signaling pathway. After the effector is engaged and the signal is set in motion, the alpha subunit’s own GTPase activity hydrolyzes GTP to GDP, which allows the alpha subunit to reassociate with the beta-gamma dimer and reset the system. This sequence—alpha-GTP moving to the effector and activating it, followed by GTP hydrolysis to GDP and reassembly with beta-gamma—best fits how GPCR signaling is turned on and then terminated. The other options don’t match this flow: the GTP-bound subunit doesn’t bind a second receptor, receptor internalization isn’t the immediate next step, and GTP is not converted directly into ATP in this process.