Pepsin

Definition

Pepsin is an enzyme that breaks down proteins into smaller peptides. It is produced in the stomach and is most active in acidic environments.

5 Must Know Facts For Your Next Test

1. Pepsinogen, the inactive precursor of pepsin, is secreted by chief cells in the stomach lining.
2. Hydrochloric acid (HCl) in the stomach converts pepsinogen to its active form, pepsin.
3. Pepsin specifically cleaves peptide bonds involving aromatic amino acids like phenylalanine, tryptophan, and tyrosine.
4. The optimal pH for pepsin activity is around 1.5 to 2.0.
5. Pepsin plays a crucial role in the initial stages of protein digestion before chyme moves to the small intestine.

Review Questions

• What is the primary function of pepsin?
• How is pepsinogen activated into pepsin?
• Why does pepsin require an acidic environment to function effectively?

Related terms

Hydrochloric Acid (HCl): A strong acid produced by parietal cells in the stomach that helps create an acidic environment necessary for pepsin activation.

Chief Cells: Specialized cells in the stomach lining that secrete pepsinogen.

Chyme:

The semi-fluid mass of partly digested food expelled by the stomach into the small intestine.