Скачать или смотреть 2. Digestion of Dietary Proteins & Absorption of Amino Acids | Medical Biochemistry | USMLE Step 1

𝐒𝐮𝐛𝐬𝐜𝐫𝐢𝐛𝐞 𝗙𝐨𝐫 𝗠𝐨𝐫𝐞 𝗜𝐧𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝗛𝐞𝐚𝐥𝐭𝐡 👩‍⚕‍ 𝐚𝐧𝐝 𝗠𝐞𝐝𝐢𝐜𝐢𝐧𝐞💉🩺💊
📌𝗜𝗻𝘀𝘁𝗮𝗴𝗿𝗮𝗺 :   / clinical.learning  

Digestion of Dietary Proteins & Absorption of Amino Acids | Medical Biochemistry | MBBS 1st Year | USMLE Step 1

👋 Hey future doctors and biochem learners! Proteins from our diet — meat, milk, eggs, pulses — cannot be absorbed as such. They must first be digested into amino acids and small peptides before absorption in the intestine. This process involves the stomach, pancreas, intestinal enzymes, and specialized transporters.

In this lecture, we’ll cover the step-by-step breakdown of dietary proteins, the enzymes involved, absorption mechanisms, and clinical correlations. A must-know for MBBS, NEET PG, FMGE, and USMLE Step 1! 🧬📚

🌟 Digestion of Dietary Proteins

1️⃣ Gastric Phase (Stomach)

Enzyme: Pepsin (secreted as pepsinogen, activated by HCl).

Breaks proteins into large peptides.

Denaturation by gastric acid aids enzymatic action.

2️⃣ Pancreatic Phase (Small Intestine – Lumen)

Pancreas secretes inactive zymogens (trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidases).

Activated in the intestine by enterokinase (enteropeptidase) → activates trypsin, which activates other proteases.

Breakdown into oligopeptides & amino acids.

3️⃣ Intestinal Phase (Brush Border Enzymes)

Peptidases at the brush border (dipeptidases, aminopeptidases) further degrade peptides into amino acids, dipeptides, tripeptides.

🌟 Absorption of Amino Acids

Occurs mainly in proximal small intestine.

Na⁺-dependent active transporters carry amino acids across enterocytes.

Different transporters exist for neutral, basic, acidic, and imino acids.

Small peptides absorbed by PEPT1 transporter and hydrolyzed inside enterocytes.

Amino acids released into the portal circulation to the liver.

🩺 Clinical Correlations

Cystinuria: Defective transport of cystine, ornithine, lysine, arginine (COLA) → kidney stones (hexagonal crystals).

Hartnup Disease: Defect in neutral amino acid transport (e.g., tryptophan) → niacin deficiency → pellagra-like symptoms (dermatitis, diarrhea, dementia).

Pancreatic insufficiency (chronic pancreatitis, cystic fibrosis): ↓ protease secretion → protein malabsorption.

Zollinger–Ellison syndrome: Excess gastric acid inactivates pancreatic enzymes → maldigestion.

🎯 Exam Integration

Pepsin = stomach, acidic pH.

Trypsin = key activator of pancreatic zymogens.

Na⁺-dependent amino acid transporters = essential for absorption.
👉 High-yield in case vignettes involving malabsorption, renal stones, and metabolic deficiencies.

👉 Don’t forget to Subscribe and ring the 🔔 bell for more high-yield medical biochemistry lectures!

👍 If this lecture helps you, give it a like and share it with your classmates. Your support keeps us motivated to create simplified, exam-focused content. 🙌

❓Want us to make a separate lecture on clinical disorders of amino acid absorption (Cystinuria, Hartnup disease, etc.)? Drop your request in the comments below! 😊

#ProteinDigestion #AminoAcidAbsorption #MedicalBiochemistry #USMLEStep1 #MBBSLectures #FMGE #NEETPG #Pepsin #Trypsin #Enteropeptidase #Cystinuria #HartnupDisease #ProteinMetabolism #PancreaticInsufficiency #ZollingerEllison #BiochemistryLecture #MedicalStudents