- Most abundant protein in the body (30% of dry weight)
- 4 Categories according to structure/function:
i. Form long fibrils
ii. Fibril-associated collagens (bind collagen fibers to extracellular matrix)
iii. Form anchoring fibrils (e.g., attach basal lamina to underlying reticular fiber layer)
iv. Form networks (e.g., basal lamina)
- 1-20 micrometers in diameter, indeterminate length, unbranched
-
fibers are wavy in tissues, provides some capacity for stretch even
though the
actual fibers are relatively inelastic
-
Divisions of Collagen Fiber: Fiber
®
Fibril ® Microfibril =
Tropocollagen
Molecule
-
Tropocollagen molecule composed of 3 polypeptide chains forming a
right-
handed superhelix
-
Tropocollagen molecules staggered giving periodic striations to
fibril (only
visible under EM). Periodicity of striations = 64 nm (approx. 25% of length
of
tropocollagen molecule).
SEE HANDOUT