The G-protein-linked receptor is located in the plasma membrane. When GDP is attached to the G protein the messenger is considered inactive. GTP replaces GDP and now the messenger is considered active. The G protein carrying the GTP leaves the receptor and binds to and enzyme which causes a cellular response. All of this is brought on by a _______ ________ attaching to the G-protein-linked receptor and will shut down quickly when the ___________ ____________ is no longer there.
