So the digestive enzymes inside our stomach, for example, aren't always functioning. But as soon as we ingest food, those enzymes are activated by proteolytic cleavage, by other protease molecules. So these are the three major reasons as to why we have to be able to break a peptide bond. Now, the next question is why do we have to use a catalyst? Why do we need to use an enzyme for this reaction to actually take place inside our body? Well, as it turns out, as we'll see in just a moment, the rate at which the reaction takes place is very, very low.