So one of the phosphorylated tyrosine residues on the insulin receptor more specifically this one over here basically attracts a protein called the insulin receptor substrate or simply IRS. And once the IRS and in this particular case, we call it IRS One because we actually have another one called IRS Two which exists in a different pathway that we're not going to look in this lecture. But IRS One basically attaches onto this phosphorylated residue and once it is attached because it moves in close proximity to the active side of that activated receptor kinase. This green structure, the IRS itself is phosphorylated at four tyrosine residues. So upon binding, the IRS itself is phosphorylated by the insulin receptor kinase. Now, what is the point of asphorylating this region?