When a G-protein linked receptor is activated, the first thing that happens is that a [Select] binds to the receptor. Before this binding happens, a G-protein with [Select] bound to it is replaced with a G-protein now with [Select] bound to it. When this G-protein activates an enzyme, the [Select] attached to the G-protein is used and is converted to [Select]. One example of an enzyme that can be activated by a G-protein is [Select]. When this enzyme is activated, it can convert [Select] into [Select], which is known as a second messenger. When it is used as a second messenger, it activates an enzyme called [Select], which then activates a transduction pathway. Finally, the enzyme [Select] is used to convert this second messenger molecule.