Hydrochloric Acid

What is Hydrochloric Acid?

An acid secreted by the wall of the stomach. It has two functions: it provides the acidic conditions in which stomach protease works best, and it kills many of the microorganisms that are swallowed with food. It is not an enzyme and does not itself digest protein.

This definition is part of the Human Nutrition chapter in Cambridge O Level Biology.

Concepts related to Hydrochloric Acid

• stomach
• Protease
• Optimum pH
• Denaturation

Common mistakes with Hydrochloric Acid

• “Hydrochloric acid digests the protein in the stomach.” Why it is wrong Acid is not a catalyst and is not an enzyme. It creates the conditions in which the stomach's protease works, and it kills many ingested microorganisms. Write instead "Hydrochloric acid provides the acidic conditions the stomach protease needs, and kills many ingested microorganisms. The protease does the digesting."