PEPSIN IS SECRETED AS AN INACTIVE PRECURSOR CALLED PEPSINOGEN BECAUSE

• A. pepsin as an enzyme is quickly destroyed by the alkaline food from the mouth
• B. all digestive enzymes pass through a precursor stage ✓
• C. pepsin is a proteolytic enzyme and might attack the stomach tissues
• D. pepsin is not required in large quantities

Pepsin is secreted as an inactive precursor called pepsinogen because all digestive enzymes pass through a precursor stage. This is a common mechanism in the body to prevent the premature activation of enzymes that could potentially harm the tissues they are meant to work on. Pepsinogen is produced by the chief cells in the stomach lining and is then converted into its active form, pepsin, by the acidic environment of the stomach.

When food enters the stomach, it triggers the release of hydrochloric acid, which lowers the pH of the stomach contents. This acidic environment is essential for activating pepsinogen into pepsin. Pepsinogen is activated by hydrochloric acid through a process called autocatalysis, where pepsin itself helps convert more pepsinogen into active pepsin.

If pepsin were secreted directly as an active enzyme without being in its inactive form first, it could lead to premature digestion and damage to the stomach tissues. By producing pepsin as an inactive precursor, the body ensures that it is only activated when it reaches the appropriate location with the right conditions for digestion to occur.

In summary, pepsin is secreted as an inactive precursor called pepsinogen because all digestive enzymes go through a precursor stage to prevent damage to tissues and ensure they are activated at the right time and place for optimal digestion.