Final answer:
Enzyme supplements taken by mouth may not be effective due to the denaturing effect of stomach acid (HCl), which can render them nonfunctional before they reach the small intestine where digestion continues. Option 2 is correct answer.
Step-by-step explanation:
Taking enzyme supplements by mouth may not be useful for several reasons, particularly because many enzymes are denatured by HCl in the stomach. Enzymes are proteins, and like other proteins, they can be unfolded or denatured when exposed to the highly acidic environment of the stomach where hydrochloric acid (HCl) is present. This denaturation process breaks down the enzyme's structure, rendering it nonfunctional.
While it is true that our bodies naturally produce enzymes, and that bile emulsifies lipids in the small intestine, the critical reason enzyme supplements might not be effective when taken orally is that the acidic conditions of the stomach can degrade the proteins (enzymes) before they reach the small intestine where they could act on food substances.
Summary of digestion processes:
1) Protein digestion begins in the stomach with the action of HCl and pepsin and is completed in the small intestine.
2) Lipids are largely undigested when they arrive in the small intestine and are emulsified by bile, which is necessary for the digestion of lipids because they do not dissolve in the watery chyme.
3) Enzyme supplements intended for other functions can be broken down in this acidic environment and thus be ineffective.
In conclusion, the most accurate reason enzyme supplements taken orally may not be useful is that they can be denatured in the stomach by HCl, which is option 2.