Final answer:
Pepsin is an animal-derived enzyme in the stomach that breaks down proteins into peptides, aiding in protein digestion. It acts specifically on peptide bonds of aromatic amino acids and functions in an acidic environment. Proteins are ultimately broken down into amino acids for absorption in the small intestines.
Step-by-step explanation:
Pepsin is an enzyme primarily found in the stomach of animals that is responsible for digesting proteins. It breaks down proteins into smaller units known as peptides, specifically targeting peptide bonds contributed by aromatic amino acids like tyrosine, tryptophan, and phenylalanine. Pepsin works in an acidic environment, where it helps speed the reaction of protein digestion by cleaving these proteins into peptides, which are then further broken down into amino acids that can be absorbed into the bloodstream through the small intestines. Following the stomach's role in protein digestion, other enzymes such as trypsin, elastase, and chymotrypsin, produced by the pancreas and released into the duodenum, continue the process reducing the peptides into even smaller peptides and ultimately into free amino acids. The substrate for pepsin is the intact protein, and some of the products of the reaction that pepsin catalyzes are these shorter peptide chains. Pepsin is a natural enzyme that originates from animal tissue and is not found in plants, minerals, synthetics, or produced directly via recombinant DNA techniques for its digestive functions.