So basically what happens is we have the epinephrine, we have the transmembrane protein, our protein that basically goes on from the outside to the inside of the cell through the membrane shown in green. And on the inner portion of the membrane, on the cytoplasmic side of this transmembrane, known as beta adrenergic receptor we basically have a complex of other proteins. We have the alpha subunit, the beta subunit and the gamma subunit. And the alpha subunit, as we'll see, is our G protein. So on a different section of that membrane we have another type of protein that is involved in this activation process. In the secondary messenger system process, this is known as the adenylate cyclase protein.