In the stomach: a. pepsin converts hydrochloric acid to pepsinogen b. pepsin converts pepsinogen to hydrochloric acid c. hydrochloric acid converts pepsinogen to pepsin d. hydrochloric acid converts pepsin to pepsinogen
The Correct Answer and Explanation is:
The correct answer is c. hydrochloric acid converts pepsinogen to pepsin.
Explanation:
The stomach plays a critical role in the digestion of proteins, and this process is facilitated by the enzyme pepsin, which is initially produced as an inactive precursor called pepsinogen. Pepsinogen is secreted by the chief cells of the stomach lining. However, pepsinogen itself is inactive and cannot digest proteins until it is converted into its active form, pepsin.
This conversion is facilitated by hydrochloric acid (HCl), which is secreted by the parietal cells of the stomach. When hydrochloric acid comes into contact with pepsinogen, it lowers the pH in the stomach. The acidic environment (with a pH of around 1.5 to 3.5) causes pepsinogen to undergo a conformational change, leading to the activation of pepsin. Once activated, pepsin can begin breaking down proteins into smaller peptides, aiding in digestion.
This mechanism is a key step in protein digestion because it ensures that pepsin is only active in the stomach, where it is needed. In the absence of HCl or if pepsinogen were to be activated prematurely, pepsin could potentially damage the stomach lining. This is why it is crucial for pepsinogen to remain inactive until it is exposed to hydrochloric acid.
Thus, the correct physiological sequence is: Hydrochloric acid (HCl) converts pepsinogen to pepsin, enabling the digestion of proteins.
