What role does the small intestine play in protein digestion?

The small intestine plays a crucial role in the final stages of protein digestion. While protein digestion begins in the stomach through the action of pepsin and hydrochloric acid, the small intestine is where the majority of protein breakdown occurs. In the small intestine, pancreatic enzymes such as trypsin, chymotrypsin, and carboxypeptidase, as well as brush border enzymes, further digest proteins into smaller peptides and amino acids.

As food passes through the small intestine, these enzymes act to complete the digestion process, breaking down the peptides into their constituent amino acids which can then be absorbed through the intestinal walls into the bloodstream. This absorption is vital as amino acids serve as building blocks for various bodily functions, including tissue repair and the production of enzymes and hormones.

Thus, the small intestine is essential in completing the digestion of proteins, making it clear why the correct answer reflects its critical role in this process.