For each of the following sentences, select the best word or phrase from the list below to fill in the blanks. Not all words or phrases will be used; each word or phrase should be used only once

Question

G-protein-coupled receptors (GPCRs) all have a similar structure with __________________ transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of __________________ subunits, becomes activated. __________________ of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the ? subunit is bound to __________________, which is exchanged for __________________ on stimulation. The intrinsic __________________ activity of the ? subunit is important for inactivating the G protein. __________________ inhibits this activity of the ? subunit, thereby keeping the subunit in an active state.

adenylyl cyclase cholera toxin GTPase
AMP diacylglycerol phosphodiesterase
ATP five seven
ATPase four three
Ca2+ GDP twelve
cAMP GTP two


Fill in the blank(s) with correct word

Answer 1

G-protein-coupled receptors (GPCRs) all have a similar structure with seven transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of three subunits, becomes activated. Two of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the ? subunit is bound to GDP, which is exchanged for GTP on stimulation. The intrinsic GTPase activity of the ? subunit is important for inactivating the G protein. Cholera toxin inhibits this activity of the ? subunit, thereby keeping the subunit in an active state.