Pepsin is an enzyme secreted into the stomach. Which macromolecule does it
function in breaking down?

A. Carbohydrates
B. lipids
C. proteins
D. nucleic acids

C. proteins

Explanation: In humans, ingested proteins are degraded into their constituents amino acids in the stomach. When dietary protein enters into the stomach, it stimulates the gastric mucosa to secrete the hormone gastrin.

Gastrin in turn stimulates the chief cells of the gastric glands to secrete pepsinogen. Pepsinogen is an inactive precursor or zymogen that is then converted to active pepsin through enzymatic cleavage.

Pepsin hydrolyzes the peptide bonds of the ingested proteins proteins at the amino terminal side of aromatic amino acid residues such as phenylalanine, tryptophan and tyrosine, cleaving long polypeptide chains into a mixture of smaller peptides.