Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Pepsin is an enzyme in the stomach that breaks down proteins into smaller peptides. It is activated from its precursor, pepsinogen, in the acidic environment of the stomach.
5 Must Know Facts For Your Next Test
Pepsin is produced by chief cells in the stomach lining.
It is most active at a pH of 1.5 to 2.
Pepsinogen is converted to pepsin when it encounters hydrochloric acid (HCl) in the stomach.
Pepsin primarily breaks peptide bonds between amino acids phenylalanine, tryptophan, and tyrosine.
Inadequate pepsin activity can lead to protein malnutrition.
Review Questions
Related terms
Gastric Juice: A mixture of hydrochloric acid, enzymes including pepsin, and mucus secreted by the stomach lining.
Chief Cells: Cells located in the stomach lining that release pepsinogen.
Hydrochloric Acid (HCl): A component of gastric juice that activates pepsinogen into pepsin and maintains a low pH in the stomach.