Now, Ras is a small g protein and once this binding takes place, it essentially constricts this space and allows this molecule to expel the GDP guanosine diphosphate and instead it buys a peak guanosine triphosphate and that activates this Ras protein. So in step three we have the SOS then binds Ras, a small g protein. This activates Ras by expelling a GDP and binding instead a GTP. Now, this Ras is actually attached into the membrane and that's because the Rasp protein contains a covalently modified amino acid that contains a lipid attachment and that lipid attachment remains inside the membrane. Now, once the Ras is in its inactive form, it goes on to activate another membrane, membrane bound protein known as RAF. And just like this structure contains the covalently modified lipid, this structure also contains a covalently modified lipid component that is found within the membrane.