Why is HCl required in the stomach?
A. To transport proteins into the small intestines
B. To help absorb other acids in the stomach
C. To catalyze the digestion of carbohydrates
D. To aid in the digestion of proteins
The correct answer is D. To aid in the digestion of proteins.
HCl, or hydrochloric acid, is required in the stomach to help with the digestion of proteins. When we consume food, the stomach produces HCl to create an acidic environment. This acidic environment activates an enzyme called pepsinogen, which is produced by the stomach cells. In the presence of HCl, pepsinogen is converted into pepsin, an active enzyme that breaks down proteins into smaller polypeptides. These polypeptides can then be further broken down into individual amino acids by other digestive enzymes in the small intestine.
To arrive at this answer, you can eliminate choices A, B, and C by understanding their functions in relation to the stomach. The transportation of proteins into the small intestines is not regulated by HCl in the stomach but rather by other digestive processes in the intestines. Absorption of other acids in the stomach is also not a function of HCl. Lastly, the digestion of carbohydrates primarily begins in the mouth with the enzyme amylase and continues in the small intestine with additional enzymes, but HCl does not play a direct role in this process. Therefore, D is the most appropriate answer.