They are used to break down and recycle the proteins found inside our cells. And finally, as we'll discuss in much more detail in the future, these proteases are also actually used in proteolytic cleavage and that is used to activate or sometimes deactivate important biological pathways and biological molecules. So as we'll see in the future lecture, these different types of digestive enzymes are actually themselves activated by other proteases. 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.