Well, the two alpha units, which are, by the way, found on the outside of the cell, the extracellular environment basically create the pocket, the region of space that binds the insulin. And so that exists on the outside of the cell. Now, these beta submunes not only spam the entire membrane shown here, but they also have components found on the inside the cytoplasmic side of the cell. And these two regions of the beta soviets basically contain a very important section that gives this receptor its activity. And this section contains the tyrosine protein kinase domains. Now, a tyrosine protein kinase is basically an enzyme, a protein that phosphorylates tyrosine amino acids on target proteins and enzymes.