The acid in gastric juice is

Gastric juice is a digestive fluid produced by the gastric glands located in the stomach wall [1]. The primary acidic component of this juice is hydrochloric acid (HCl), which is secreted by specialized epithelial cells known as parietal cells. Hydrochloric acid serves several critical functions: it creates a highly acidic environment (typically pH 1.5 to 3.5) that facilitates the activation of the protein-digesting enzyme pepsin from its inactive precursor, pepsinogen [1]. Additionally, the strong acidity of HCl helps in denaturing proteins and acts as a protective barrier by killing many harmful bacteria and pathogens ingested with food [4]. While the stomach produces this strong acid, the inner lining is protected from self-digestion and damage by a layer of alkaline mucus [4]. Other acids like acetic, nitric, or sulphuric acid are not naturally occurring components of human gastric secretions.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.3 > p. 85
2. [4] https://www.ncbi.nlm.nih.gov/books/NBK537005/