And let's begin by examining the structure of this g coupled protein receptor before that primary messenger actually binds onto its site. So we have the membrane, we have the inside the cell, the outside of the cell. On the outside the cell, we have this cavity that basically binds the primary messenger. On the posing side, the intracellular side, we have a trimmer structure that is bound onto that seven TM structure. And this trimer consists of three different types of domains. We have the gamma domain shown in blue.