Abdul Basit Official

📌 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. 🧬📖