Gastrointestinal | Digestion & Absorption of Proteins

Official Ninja Nerd Website: https://ninjanerd.org Ninja Nerds! In this lecture, Professor Zach Murphy will present on the digestion and absorption of proteins. We begin by discussing the initial steps of protein breakdown in the stomach, where gastric chief cells secrete pepsinogen, which is activated to pepsin by the acidic environment created by parietal cell secretion of hydrochloric acid. This stage initiates the hydrolysis of large polypeptides into smaller peptide chains. From there, we move into the small intestine, where pancreatic proteases—including trypsin, chymotrypsin, elastase, and carboxypeptidases—continue protein breakdown. We explain the activation cascade starting with enterokinase in the duodenal brush border, which converts trypsinogen to trypsin and activates other proteases. The resulting oligopeptides are digested by brush border peptidases into dipeptides, tripeptides, and free amino acids. Finally, we explore the mechanisms of absorption into enterocytes. Amino acids are transported via sodium-dependent carriers, while dipeptides and tripeptides use proton-linked transporters and are subsequently hydrolyzed to amino acids within the cell. These amino acids then enter the portal circulation to reach the liver. Enjoy the lecture and support us below! 🌐 Official Links Website: https://www.ninjanerd.org Podcast: https://podcast.ninjanerd.org Store: https://merch.ninjanerd.org 📱 Social Media   / ninjanerdlectures     / ninjanerdlectures     / ninjanerdlectures   https://x.com/ninjanerdsci/   / ninja-nerd   💬 Join Our Community Discord:   / discord   #ninjanerd #DigestionofProteins #Gastrointestinal