Final answer:
The low pH of the stomach aids in protein digestion by activating the enzyme pepsin and providing a hostile environment for ingested pathogens.
Step-by-step explanation:
The low pH of the stomach serves an important role in the digestion of proteins. This acidic environment is critical for the proper functioning of digestive enzymes like pepsin, which break down protein molecules into smaller peptides and amino acids. At the same time, the high acidity helps to kill harmful microorganisms that may be ingested with the food.
Protein digestion begins in the stomach, where hydrochloric acid (HCl) and pepsin work together to denature and fragment proteins. The denaturation process unfolds protein molecules, exposing the peptide bonds for enzymatic cleavage by pepsin. Pepsin operates optimally at a low pH range, specifically around 1.5, efficiently processing proteins into smaller peptides. The stomach's acidity thus plays a dual role, both in aiding protein digestion by activating and supporting the action of pepsin and in providing a protective barrier against pathogens.