If the cell needs to synthesize proteins or nucleotide bases, then we can use these amino acids for that. But if the cell needs to use the amino acid for energy, what it can do is it can remove the carbon skeleton. It could remove that urea via the urea cycle and we'll talk about that in more detail. And then the carbon skeleton can basically be used to generate energy as we'll talk about in more detail in a lecture to come. So we see that once we ubiquitate that particular protein, only then can the protein can actually bond to the special proteasome complex. So the proteasome complex consists of the 19s regulatory submit that recognizes that target protein and prevents the other normal proteins that have not been ubiquitated from actually being broken down within this core.