So the small RNA molecule helps form the signal recognition particle that directs the synthesized protein to their intracellular or extracellular final destination. Let's move on to small interfering RNA molecules or siRNA molecules. And what these molecules do is they essentially bind onto the mRNA molecule and they stimulate the breakdown, the degradation of the messenger RNA molecule. So remember we don't always want to synthesize a given protein inside our cells because first of all protein synthesis uses up a lot of ATP molecules. And so if we have plenty of a given polypeptide in our cell we don't actually want to synthesize anymore. So at times we want to break down our messenger RNA molecule and it's the small interfering RNA that helps break down and stimulate the breakdown of the messenger RNA molecule.