What is the role of pepsin in protein digestion?

Pepsin plays a critical role in protein digestion by breaking down proteins into smaller chains called polypeptides. This enzyme, which is secreted in an inactive form known as pepsinogen, is activated in the acidic environment of the stomach. Once activated, pepsin begins the process of hydrolyzing the peptide bonds that link amino acids together in protein molecules.

This breakdown process is essential because it prepares proteins for further digestion in the small intestine, where enzymes continue to dismantle these polypeptides into even smaller peptides and eventually into amino acids that can be absorbed by the body. The action of pepsin thus represents the initial step in the complex journey of protein digestion, laying the groundwork for more thorough breakdown and nutrient absorption downstream.

The other options do not pertain to the role of pepsin. Nutrient absorption occurs primarily in the intestines, emulsification of fats is a function typically performed by bile and lipases, and the digestion of starches is handled by different enzymes, not pepsin.