29/06/2026
📌 Digestion & Absorption of Protein – Key Points
🔹 Protein digestion begins in the stomach and is completed in the small intestine.
🔹 No chemical digestion of proteins occurs in the mouth; chewing only breaks food into smaller particles.
🔹 Hydrochloric acid (HCl) denatures proteins and activates pepsinogen → pepsin.
🔹 Pepsin is an endopeptidase that converts proteins into smaller polypeptides.
🔹 In the duodenum, enteropeptidase (enterokinase) activates trypsinogen → trypsin.
🔹 Trypsin activates other pancreatic zymogens:
Chymotrypsin
Elastase
Carboxypeptidases A & B
🔹 Brush border enzymes (aminopeptidase, dipeptidase, tripeptidase) complete protein digestion.
🔹 Final digestion products:
✅ Free amino acids
✅ Dipeptides
✅ Tripeptides
🔹 Free amino acids are absorbed by Na⁺-dependent transporters.
🔹 Dipeptides and tripeptides are absorbed by the H⁺-dependent PEPT1 transporter.
🔹 Most dipeptides and tripeptides are converted into free amino acids inside enterocytes.
🔹 Amino acids enter the hepatic portal vein and are transported to the liver.
📚 Regulation
Gastrin → Stimulates HCl and pepsinogen secretion.
Secretin → Stimulates bicarbonate secretion from the pancreas.
CCK → Stimulates pancreatic enzyme secretion and slows gastric emptying.
⭐ Major Sites
Digestion: Stomach & Small Intestine
Absorption: Jejunum & Ileum
Caption idea:
> Protein digestion is a coordinated process involving gastric acid, pancreatic enzymes, brush border peptidases, and specialized transporters, ensuring efficient absorption of amino acids for growth, repair, and metabolism. 🧬📖
