Question

Ll G-proteins are active when bound to (1) and inactive when bound to (2).

A) GDP; GTP
B) GTP; GDP
C) ATP; ADP
D) ADP; ATP

Answer 1

G-protein-linked receptors are proteins involved in cell signaling. When a hormone binds to the receptor, the G-protein is activated and exchanges GDP for GTP. After a while, GTP is hydrolyzed back to GDP, deactivating the G-protein. Option number b is correct.

Step-by-step explanation:

G-protein-linked receptors are proteins found in the cell membrane that are involved in cell signaling. When a hormone or ligand binds to the receptor, the G-protein associated with the receptor is activated.

The inactive G-protein is bound to guanosine diphosphate (GDP), but upon activation, it releases GDP and picks up guanosine triphosphate (GTP), which activates the G-protein. After a while, the GTP on the active subunit of the G-protein is hydrolyzed back to GDP, resulting in deactivation of the G-protein. The subunits then re-associate to form the inactive G-protein, starting the cycle anew.