And those additional structures play very important, very specific roles. So now let's move on to the epinephrine signaling pathway. So in the epinephrine signal transduction pathway, the epinephrine is that primary messenger and binds into a special region of a protein we call the beta adrenergic receptor, the beta AR, which is a type of seven TM receptors. So this is what it looks like. So we have the membrane, we have the outside, the inside. This is the epinephrine shown in red.