Collagen

James Carmichael, 2008

Introduction

• The most abundant extra-cellular protein in the human body
• Makes up 30% of total body protein

Synthesis

• Protein synthesis on the endoplasmic reticulum forms three polypeptide chains that make up protocollagen
• Hydroxylated to procollagen
• Procollagen is then converted to a triple helix and then secreted from the cell
• Once secreted procollagen pepsidases split off the terminal endieces to allow polymerisation.
• It is these crosslinks that determine the tensilestrength.

Structure

• A collagen molecule is a triple helix made up of 3 alpha chains (2 alpha 1 and 1 alpha 2)

 
Types of Collagen:

1. bone, tendon, meniscus, annulus of intervertebral disc, skin
2. Articular cartilage, Nucleus propulsus
3. Skin, Blood vessel
4. Basement Membrane
5. Articular cartilage (small amounts)
6. Thethers condrocytes to the ECM in articular cartilage
7. Epithelial Basement Membrane
8. Epithelial basement membrane
9. Articular Cartilage (small amounts)
10. Hypertrophic cartilage
11. Articular Cartilage (small amounts)
12. Tendon
13. Endothelial cells

These collagens are broadly divided into 3 classes

Class 1: These have long chains and are the orthopaedic collagens
                Types I, II and III

Class 2: Basement membrane components 
                Types IV, VII and VIII

Class 3: Miscellaneous 
                Types VI, IX and X

Collagen Function

The function collagen performs is related to its structure and is subtly different in different tissues

Type 1 Collagen:

Type 1 collagen is usually responsible for resisting tensile forces. In this manner it contributes to the function of the tissues it is found in.