So Ubiquitin is this marker for those proteins that needs to be broken down. And before the protein is actually broken down, it undergoes a process known as Ubiquit nation. That is, we attach many Ubiquitant molecules onto that target protein that needs to be broken down. 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.