What activates pepsinogen in the stomach?

Pepsinogen is an inactive enzyme precursor (zymogen) that is secreted by the gastric chief cells in the stomach. It requires activation to convert into its active form, pepsin, which is essential for the digestive process. The activation of pepsinogen primarily occurs in the presence of hydrochloric acid (HCl) that is secreted by the gastric parietal cells.

When food enters the stomach, the secretion of HCl leads to a decrease in pH, creating an acidic environment. This acidic pH is crucial as it not only denatures proteins, aiding in digestion, but also catalyzes the conversion of pepsinogen into pepsin. The activated pepsin can then begin the process of protein digestion by breaking down the peptide bonds in proteins, further enhancing the digestive process.

While pepsin does play a role in the digestion of proteins, it is not the primary activator of pepsinogen; rather, it is produced as a result of pepsinogen activation. Carbonic acid is not involved in this activation process, and trypsin, another enzyme involved in protein digestion found mainly in the small intestine, does not play a role in the stomach's activation of pe