Can you be more specific to the question
I think the system you are referring to is the muscular system
Pepsin is an Enzyme that is found in the stomach to break down protein.The Pepsin breaks the protein down into smaller peptides at low pH vale.
There is also one within the small intestine called Chymotrypsin and also the Carboxypeptidase.
Hope this helps and if you are still unsure read up on these to help you.
The nucleus is particularly important among eukaryotic organelles because it is the location of a cell's DNA. Two other critical organelles are mitochondria and chloroplasts, which play important roles in energy conversion and are thought to have their evolutionary origins as simple single-celled organisms.
