What substances are contained in gastric juice? What are their functions?

(N/A) Gastric juice contains three main substances: hydrochloric acid, the enzyme pepsin, and mucus.
Functions:
$1$. Hydrochloric acid: It creates an acidic medium in the stomach, which is necessary for the activation of the enzyme pepsin. It also kills harmful bacteria ingested with food.
$2$. Pepsin: This enzyme breaks down complex proteins present in food into smaller peptide molecules.
$3$. Mucus: It protects the inner lining of the stomach wall from the corrosive action of hydrochloric acid.