Скачать или смотреть 13. Glycosaminoglycans (GAGs) & Proteoglycans | Structure & Functions MBBS 1st year | USMLE

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Glycosaminoglycans (GAGs) & Proteoglycans | Structure, Functions & Clinical Aspects | MBBS Biochemistry | USMLE Step 1

👋 Hey future doctors and biochem learners! Connective tissue isn’t just about collagen and elastin — it also contains glycosaminoglycans (GAGs) and proteoglycans, which form the gel-like extracellular matrix. These molecules provide support, lubrication, and resilience, and their abnormalities cause important storage diseases.

This lecture explains the structure, functions, and clinical aspects of GAGs and proteoglycans, making it a must-know topic for MBBS, NEET PG, FMGE, and USMLE Step 1. 🧬📚

🌟 Glycosaminoglycans (GAGs)

Definition: Long, unbranched polysaccharides made of repeating disaccharide units (amino sugar + uronic acid).

Characteristics: Negatively charged (due to sulfate/carboxyl groups) → highly hydrophilic → attract water → form gel-like matrix.

Major Types of GAGs & Locations:
• Hyaluronic acid – synovial fluid, vitreous humor.
• Chondroitin sulfate – cartilage, bone.
• Dermatan sulfate – skin, heart valves.
• Heparan sulfate – basement membranes.
• Heparin – anticoagulant (mast cells).
• Keratan sulfate – cornea, cartilage, bone.

🌟 Proteoglycans

Definition: Core protein + covalently attached GAG chains.

Structure: Bottle-brush appearance; multiple GAGs attached to central protein.

Functions:
• Provide compressive strength in cartilage.
• Regulate cell signaling and growth.
• Act as molecular sieves in basement membranes.

🩺 Clinical Aspects

1️⃣ Mucopolysaccharidoses (MPS) – Lysosomal Storage Disorders

Defective degradation of GAGs due to enzyme deficiencies.

Hurler syndrome (MPS I): α-L-iduronidase deficiency → coarse facies, corneal clouding, organomegaly.

Hunter syndrome (MPS II): Iduronate sulfatase deficiency → similar but no corneal clouding (X-linked).

Other types: Sanfilippo, Morquio, Maroteaux-Lamy syndromes.

2️⃣ Hyaluronic acid → therapeutic uses in joint injections, wound healing.

3️⃣ Heparin → anticoagulant used in thromboembolic disorders.

🎯 Exam Integration

GAGs = disaccharide repeats (amino sugar + uronic acid).

Proteoglycan = core protein + GAGs.

Hyaluronic acid = only GAG without sulfate.

MPS (Hurler, Hunter) = failure of GAG degradation.
👉 Favorite for both direct recall and case-based USMLE/NEET PG MCQs.

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❓Should we cover a separate lecture on Mucopolysaccharidoses (Hurler, Hunter, etc.) as the next step in your Connective Tissue playlist? Drop your request in the comments below! 😊

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