So what happens is once our first messenger binds to our transmembrane protein, on the other side of that transmembrane protein we have other proteins attached as we'll see in just a moment. And once our first messenger actually binds to our transmembrane protein it causes the dissociation of one of these proteins and usually it's the G protein. Now, once our G protein detaches, it can go on and do several things. So it can activate other protein channels, it can activate our secondary messenger molecules or it can go on and activate other enzymes and it can also go on and actually transcribe genetic information as we'll see in a future lecture when we get into biochemistry. So let's take a look at a specific secondary messenger system that involves the activation of a protein known as protein kinase A. So recall in our discussion of enzymes that protein kinase A is a special type of enzyme that catalyzes the phosphorylation of other proteins to activate those proteins.