And then this chimetryptsin can basically react with polypeptides, cleave them at specific locations in the small intestine and then we can ingest those molecules into the cells of our body. So this process is known as proteolytic cleavage or proteolytic activation. Now let's move on to reversible covalent modification. So what exactly is reversible covalent modification? Well, this is the process by which we essentially modified our enzymes in a reversible fashion. We basically add some type of group and then we can remove that same type of group.