Topic overview

Start with the big picture

The lesson follows protein digestion from the gastric phase to intestinal absorption. In the stomach, acid supports pepsin activation and protein breakdown into large peptides. In the duodenum, enteropeptidase activates trypsin, initiating a pancreatic enzyme cascade; bicarbonate helps neutralize incoming acid. Pancreatic and brush-border enzymes further break peptides down. At the intestinal surface, amino acids use sodium-dependent transport, while di- and tri-peptides enter through the H⁺-dependent PepT1 transporter. Most absorbed small peptides are hydrolyzed inside enterocytes, and amino acids leave across the basolateral membrane toward portal circulation. The topic also introduces transporter-related disorders and clinical conditions that can impair proteolysis.