What happens when pepsin enters the small intestine? a. It inhibits pepsinogen synthesis. b. It cleaves proteins into smaller peptides and some free amino acids. c. It is digested due to the high pH. d. It activates HCl. e. It denatures protein structures.
The Correct Answer and Explanation is:
The correct answer is c. It is digested due to the high pH.
Pepsin is a digestive enzyme that functions primarily in the acidic environment of the stomach, where it helps break down proteins into smaller peptides. The stomach maintains a low pH, which is essential for pepsin’s activation from its inactive form, pepsinogen, and for its optimal activity.
When pepsin moves into the small intestine, the pH of the environment increases significantly. The small intestine is much less acidic than the stomach, with a pH typically ranging from 6 to 7.5, mainly due to the presence of bicarbonate ions from the pancreas, which neutralize the stomach acid. In this less acidic environment, pepsin is no longer able to function efficiently, as it requires a low pH to maintain its active form.
The enzyme’s activity is severely diminished or halted at the higher pH of the small intestine. As a result, pepsin is eventually broken down and digested by enzymes in the small intestine, since it is no longer protected by the acidic conditions of the stomach. The protein digestion in the small intestine is continued by other proteolytic enzymes such as trypsin and chymotrypsin, which are active at the more neutral pH.
In summary, when pepsin enters the small intestine, its activity is inhibited due to the increase in pH, and the enzyme itself is eventually degraded, allowing other enzymes to take over the digestion of proteins.
