In which part of the digestive system are proteins primarily digested?

The primary digestion of proteins occurs in the stomach, where the enzyme pepsin – activated by gastric acid – begins the process of breaking down proteins into smaller peptides. The stomach provides an acidic environment optimal for pepsin activity, facilitating initial protein breakdown.

Although some protein digestion continues in the duodenum, this process is more about the completion of digestion rather than the initiation. In the duodenum, pancreatic enzymes such as trypsin and chymotrypsin, along with other digestive secretions, further process the peptides into amino acids and smaller peptides that can be absorbed.

The jejunum is involved in the absorption of the digested nutrients, including the amino acids resulting from protein digestion, but it is not the primary site where protein digestion occurs. The large intestine plays a minimal role in nutrient absorption, focusing instead on the absorption of water and electrolytes, and it does not significantly participate in protein digestion.

Therefore, the stomach is identified as the key location for the initial and significant processing of proteins, making it the correct answer.