Which enzyme is activated by HCl in the stomach to help break down food?

In the stomach, hydrochloric acid (HCl) plays a crucial role in the digestion of proteins. It activates pepsinogen, a precursor enzyme produced by the stomach lining, converting it into pepsin. Pepsin is an active enzyme that begins the process of protein digestion by breaking down complex protein structures into smaller peptides. The acidic environment created by HCl not only facilitates this activation but also provides an optimal pH for pepsin’s enzymatic activity.

While other enzymes such as amylase and lipase exist in the digestive system, they are not specifically activated by HCl in the stomach. Amylase is primarily active in the mouth and begins carbohydrate digestion, while lipase is associated with fat digestion, predominantly occurring in the small intestine. Trypsin, another digestive enzyme, is secreted in its inactive form (trypsinogen) by the pancreas and is activated in the small intestine, not the stomach. Therefore, the activation of pepsinogen to pepsin by HCl in the stomach is a key step in the digestion of proteins, making it the correct answer.