Final answer:
GTP-binding proteins, or G-proteins, consist of an alpha (a) subunit, beta (ß) subunit, and gamma (y) subunit. When a signaling molecule binds to a G-protein-coupled receptor, the GDP molecule associated with the alpha subunit is replaced by GTP, leading to the dissociation of the beta and gamma subunits and triggering a cellular response.
Step-by-step explanation:
GTP-binding proteins, also known as G-proteins, have three main parts: the alpha (a) subunit, beta (ß) subunit, and gamma (y) subunit. When a signaling molecule binds to a G-protein-coupled receptor, a GDP molecule associated with the a subunit is exchanged for GTP. This causes the ß and y subunits to dissociate from the a subunit, triggering a cellular response. The signal is terminated when GTP is hydrolyzed to GDP.