So to demonstrate why this is actually true, let's take a look and summarize the four different pathways that we discussed so far. And let's begin by discussing what types of protein kinases are used by the four different types of pathways that we discussed up to this point. So let's begin with the epinephrine signaling pathway. So remember, in our discussion of the epinephrine signaling pathway, we focused on the physiological effect of running away from an animal. We set a bear. And so we said that a kinase is used in this particular pathway, namely protein kinase A.