Explain how enzymes in the digestive system break down a protein-rich meal into molecules that can be absorbed into the blood.

Proteases are the enzymes that digest proteins. They are produced in the stomach (pepsin) and in the pancreas (trypsin, chymotrypsin, carboxypeptidase) and are also present in the small intestine. The proteases cleave the peptide bonds in the protein, breaking it down into smaller peptides and eventually into individual amino acids. These amino acids are small and soluble, so they can be absorbed across the epithelial cells of the small intestine. Once inside the enterocytes, the amino acids are transported into the blood via active transport and diffusion, allowing them to reach the body's tissues.