Protein digestion, a crucial process for obtaining essential amino acids, primarily takes place in three key locations within the digestive system: the mouth, stomach, and small intestine.
Stages of Protein Digestion
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Mouth: Chewing initiates the mechanical breakdown of protein-containing foods, increasing the surface area available for enzymatic action. While minimal chemical digestion occurs here, the process sets the stage for subsequent steps.
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Stomach: In the stomach, hydrochloric acid (HCl) denatures proteins, unfolding their complex structures to make them more accessible to enzymes. The enzyme pepsin, activated by HCl, begins breaking down proteins into smaller peptides.
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Small Intestine: The small intestine is where the majority of protein digestion occurs. Pancreatic enzymes, such as trypsin, chymotrypsin, and carboxypeptidase, further break down peptides into smaller units, including individual amino acids. Brush border enzymes within the small intestine's lining complete the breakdown, resulting in free amino acids ready for absorption.
Absorption
Following digestion, individual amino acids and small peptides are absorbed through the intestinal lining into the bloodstream. These amino acids are then transported to the liver and subsequently utilized by cells throughout the body for various functions, including building and repairing tissues, synthesizing hormones and enzymes, and supporting immune function.
References Supporting Information: Multiple sources confirm that protein digestion occurs in the mouth, stomach, and small intestine, with the small intestine being the primary site. Specific enzymes involved in each stage are identified in these resources: Healthline, LibreTexts, Study.com.
