Unformatted text preview: collagen fibers.
Collagen protein is SLIGHTLY BASIC -- hence acidophilia of its staining. LONG CABLES w/ cross striation in TEM!!!! By transmission EM, collagen can be
seen as many individual or bundled
fibers, with each fiber having alternating
light and dark bands in longitudinal view.
long. transverse cut Fig. 5-8 There are 28 genes for collagen types,
with type I collagen the most common.
Type I collagen synthesis is best known.
These protein subunits combines in diff ways to make
about 12 diff types of Collagen ﬁbers! • Translation of mRNA for preprocollagen
occurs on RER; every 3rd amino acid is
• Hydroxylation of prolines and lysines
• Glycosylation of hydroxylysines
• Assembly of triple helix of procollagen
• Secretion of procollagen by exocytosis
• Enzymatic trimming of ends to form
• Self-assembly of these into a large
collagen fibril (with alternating light and
Glycine = smallest AA. imp. for its
helical structure….! The enzyme that does this
requires VITAMIN C!!! So if
VitC deﬁcient, you can't
maintain your CT..!! these are then secreted
to outside of cell Procollagen gets ENDS TRIMMED to form collagen subunit
rods -- these rods then self-assemble outside of cell and give
rise to BUNDLES of COLLAGEN FIBRILS IMP .. LOOK @ THIS
FIGURE!!!!! THIS IS A FIBROBLAST
DOING ALL THE WORK. Self-assembly of collagen molecules outside the fibroblasts occurs in a precise manner
that produces fibers with the alternating light and dark bands, and provides great
strength and durability to the cable-like fiber. With type I collagen the fibers are then
bundled into much larger structures shown here. With SEM, you can see
ind. FIBRILS within a
collagen BUNDLE. Fig. 5-11 Most important types of collagen and their
Type I – most common; predominates in all
forms of “CT proper”, bone, stromas &
capsules of most organs
Type II – in most cartilage
Type III (aka reticulin) – stroma of ly...
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- Spring '14
- Collagen, ground substance