It makes up about 80% of the total composition of RNA found in our cells. Now rRNA is a major constituent in the ribosomes found inside our cells and the ribosomes are the cell machinery responsible for synthesizing the polypeptide chains, the proteins. Now rRNA gives the ribosome not only its three dimensional structure but the rRNA also acts as a catalyst and it catalyzes the formation of the peptide bonds in that polypeptide chain and we'll discuss how that actually takes place in a future lecture. Now in prokaryotic cells there are three types of rRNA molecules found in the ribosome. We have the 23s, we have the we have the five S. Now in addition to these three major components of the RNA molecules found inside our body we have these additional RNA molecules that also serve their own unique function and purpose. Let's discuss what some of these RNA molecules are and let's begin with small nuclear RNA or SN RNA.