What process does pepsinogen undergo to become active pepsin?

Pepsinogen is an inactive precursor, or zymogen, produced by the gastric chief cells in the stomach. It becomes active as pepsin through a process known as proteolytic cleavage, which is facilitated primarily by hydrochloric acid (HCl). The highly acidic environment created by HCl in the stomach not only activates pepsinogen but also allows pepsin to function effectively in protein digestion.

When pepsinogen is secreted into the gastric lumen, it encounters hydrochloric acid, which lowers the pH in the stomach. At this acidic pH (around 2), pepsinogen undergoes a conformational change that leads to the removal of a small peptide sequence, resulting in the active enzyme pepsin. Pepsin is crucial for breaking down proteins into smaller peptides, a process that starts digestion before the chyme moves to the small intestine.

The other options, such as the interaction with bile, gastric mucosa, or trypsin, do not play significant roles in the activation of pepsinogen. Bile is involved in fat emulsification and digestion, gastric mucosa refers to the lining of the stomach but does not actively convert pepsinogen, and trypsin is