So let's begin by focusing on the actual structure of that protein receptor that binds the EGF molecules. And this is basically what it looks like here. So we have the cell membrane the outside and the inside of the cell. Now in its unbound state. Before the EGF molecules bind onto this receptor we see that the EGF receptor actually consists of two identical but separated monomeric units. So this is monomer number one and this is monomer number two.