Now let's take a look at the following diagram. So let's suppose this is our Ubiquitan molecule, that 76 amino acid polypeptide chain. Now on the carboxylate end of that particular molecule we have a glycine residue, a glycine amino acid, and it's this glycine amino acid that is found on the carboxylate end of that Ubiquitin that is actually attached onto that target protein that needs to be broken down. And it's the lysine residues on the target protein that are used to actually generate a bond to attach the Ubiquitin to that target protein. So suppose this is our target protein and this here is the side chain group of a lysine residue of a lysine amino acid. So we use this nitrogen on the lysine side chain group to form a bond between this nitrogen and this carbon.