Zymogens: Inactive Substances Becoming Enzymes
A zymogen refers to an inert substance that transforms into an active enzyme upon activation by another enzyme through a chemical reaction. Once activated, the enzyme assumes its functional role and begins carrying out its designated tasks. An example of a zymogen is pepsinogen, the precursor of pepsin. When the body triggers the activation of pepsinogen, it undergoes a process where it loses certain amino acids, thereby exposing catalytic sites. These sites serve as specific areas on the enzyme that can bind with molecules and initiate chemical reactions.
How Pepsinogen is Activated in the Digestion Process
Contrary to popular belief, the gastric acid present in the stomach does not directly participate in digestion. However, it does play a crucial role in the overall digestion process. When the brain detects the presence of food, the hormone gastrin is released, triggering two important events. Firstly, the cells lining the stomach secrete hydrochloric acid into the gastric acid. Secondly, chief cells in the stomach release a substance called pepsinogen. When pepsinogen comes into contact with hydrochloric acid, a chemical reaction occurs, resulting in the formation of pepsin. It is worth noting that although this reaction can take place outside the stomach, it occurs at a much slower rate.