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. So let's take a look at the following membrane. So this is the cytoplasm of our cell. This is the phospholipid bilayer of that receptor cell.