A Level Biology Practice Exam 2026 – 400 Free Practice Questions to Pass the Exam

Pepsin is classified as an enzyme, which is a type of protein that catalyzes biochemical reactions. Specifically, pepsin plays a critical role in digestion by breaking down proteins into smaller peptides in the acidic environment of the stomach. Enzymes like pepsin are essential for facilitating various physiological processes by lowering the activation energy required for reactions to occur, thus speeding them up.

In contrast to enzymes, amino acids are the building blocks of proteins, while carbohydrates serve as energy sources and structural components in living organisms. Hormones, on the other hand, are signaling molecules that regulate physiological processes but are not directly involved in catalyzing reactions like enzymes are. Thus, pepsin is distinctly classified as an enzyme due to its function and characteristics.