Скачать или смотреть 3. Connective Tissue Biochemistry | Collagen Structure, Synthesis & Clinical Aspects | USMLE Step 1

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Connective Tissue Biochemistry | Collagen Structure, Synthesis & Clinical Aspects | MBBS | USMLE Step 1

Hey future doctors and biochem enthusiasts! Did you know that collagen is the body’s main structural protein, forming the framework of skin, bone, cartilage, tendons, and blood vessels? 🦴🩺

In this lecture, we’ll dive into the structure of collagen, the step-by-step process of collagen biosynthesis, and applied clinical aspects — a topic that is high-yield for MBBS, NEET PG, FMGE, and USMLE Step 1. 🧬📚

🌟 Collagen Structure

Primary structure: Rich in glycine, proline, and hydroxyproline (Gly every 3rd residue).

Secondary/tertiary structure: Left-handed helix.

Quaternary structure: Triple helix of 3 polypeptide chains (tropocollagen).

Types of collagen:
• Type I → Bone, skin, tendon (most common).
• Type II → Cartilage.
• Type III → Reticular fibers, blood vessels (first affected in Ehlers–Danlos).
• Type IV → Basement membrane (defective in Alport syndrome, Goodpasture syndrome).

🌟 Collagen Synthesis (Stepwise)

1️⃣ In the RER (Intracellular phase):

Synthesis of pre-procollagen.

Hydroxylation of proline & lysine (requires Vitamin C).

Glycosylation of hydroxylysine.

Formation of triple helix → procollagen.

2️⃣ In the Golgi & Extracellular space:

Procollagen secreted → cleaved to tropocollagen.

Tropocollagen molecules assemble into fibrils.

Cross-linking by lysyl oxidase (requires copper) → mature collagen fibers.

🩺 Clinical Correlations

Scurvy (Vitamin C deficiency): Defective hydroxylation → weak collagen → bleeding gums, poor wound healing.

Ehlers–Danlos syndrome: Defective collagen synthesis → hyperextensible skin, hypermobile joints, vessel fragility.

Osteogenesis imperfecta: Type I collagen defect → brittle bones, blue sclera, hearing loss.

Alport syndrome: Type IV collagen defect → hematuria, hearing loss, ocular abnormalities.

Menkes disease: Copper deficiency → impaired lysyl oxidase → weak connective tissue.

🎯 Exam Integration

Mnemonic for Collagen Types: “Strong, Slippery, Stretchy, Basement” → Types I–IV.

Rate-limiting step: Hydroxylation (Vit C dependent).

Key enzymes: Prolyl hydroxylase, Lysyl hydroxylase, Lysyl oxidase.
👉 A favorite topic for both recall and clinical vignette questions in USMLE Step 1 & NEET PG.

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❓Want us to make a separate video on Collagen Disorders (Scurvy, OI, Ehlers–Danlos, Alport) with clinical cases and pathology integration? Drop your request in the comments below! 😊

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