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52 Cards in this Set

  • Front
  • Back
General contents of EM (extracellular matrix)
Protein fibers + ground substance
3 major classes of biomolecules in EM
STRUCTURAL FIBROUS PROTEIN - collagen, elastin, fibrillin
SPECIALIZED PROTEIN - fibronectin + laminin, connect structural proteins to surface of cell
PROTEOGLYCANS- 5% protein + 95% glycosaminoglycans - long chains of repeating disaccharides, GAG's, sometimes called mucopolysaccharides, major component of ground substance
Describe clinical involvement of EM
1. Metastasis - migration of cancer cells through EM
2. Inflammation - RA + OA - changes in molecular components of EM
3. Aging - many changes in matrix
Name two genetic defects of collagen
Osteogenesis imperfecta
Ehlers-Danlos Syndrome
Define collagen
family of STRUCTURALLY SIMILAR EXTRA CELLULAR GLYCOPROTEINS most of which form FIBERS OF HIGH TENSILE STRENGTH and comprise most abundant protein in animals (25-30%)
All collagen fibers are assembled from this protein
TROPOCOLLAGEN - rigid, cross linked triple helical rods
Collagens are secreted from
Fibroblasts (all types of CT)
There are _ characterized types of collagen
Which collagen type comprises 90 % of all collagens
Type I
How many chains are in collagen? Are they all the same?
There are 3 chains. In some collagens all 3 chains are the same. In some collagens, 2 chains of one type and one chain of another type
Which type of collagen is important component of basement membrane
Type IV
Describe amino acid composition of type I collagen
Glycine is every 3d amino acid, also proline and hydroxyproline
What is required to produce collagen
Oxygen, alpha ketoglutarate and vitamin C
How are chains syntesized
With signal peptide which labels them for export
How is collagen degraded
Collagenase enzymes degrade collagen and macrophages digest fragments to amino acids
Which type of collagen present in scar tissue
Type III
Describe osteogenesis imperfecta
Brittle bone disease
1/20000 births
Results in abnormal bone fragility and deformity.
Which collagen type defficient in osteogenesis imperfecta
Type I is either abnormal or reduced
Give types of OI
Type I - most common and mildest
Type II - most severe - frequently lethal short after birth
Type III and IV - intermediate severity
Describe Ehlers Danlos syndrome
1 in 10000-15000
Hyperextensibility of skin and hypermobility of joints
Most types not life threatening
Mode of inheritance for ED syndrome
Autosomal dominant or recessive, more common autosomal dominant
Mode of inheritance for OI
Autosomal dominant
Which type of ED syndrome is most severe
Vascular - leads to rupture of bowel and arteries
Which type of collagen affected in ED syndrome
Type III
Describe Alports syndrome, which collagen defective
Type IV collagen defective (basement membrane collagen)
Symptoms may include hematuria, proteinuria and kidney failure
2nd most common cause of inherited kidney failure
Most patients develop kidney failure in early adulthood and also get progressive deafness
Mostly males
Mode of inheritance for Alports
Autosomal recessive or X linked
Describe Dystrophic Epidermolysis Bullosa
Which collagen defective?
Autosomal dominant or recessive
Defect of collagen type VII that forms anchoring fibrils to keep layers of skin together.
Breakage and blistering of skin
Menke's syndrome
X linked recessive
Mutations in gene encoding copper binding ATPase
Copper enters intestinal cells but is not transported further.
Result - Cu defficiency which is required as cofactor for lysine oxidase. Fewer covalent linkages between tropocollagens are formed.
Abnormal hair and cerebral degeneration + death in early infancy
Scurvy is deficiency of what?
Vitamin C, results in defective hydroxylation of Lys and Pro residues in collagen chains, making collagen instable
Define elastin
Forms fibers of rubbery nature, confers elasticity on tissue
Elastin is prevalent where?
Walls of arteries
Elastic ligaments
Elastin is synthesized by
Williams syndrome
spontaneous mutation - 1/20000 births
Developmental disorder affecting CT in CNS
90% patients have deletions in elastin gene, resultin in insufficient elastin and narrowing of large elastic arteries - causes aortic stenosis
Alpha 1 antitrypsin defficiency
Autosomal recessive - 1 in 2500 births in Northern Europeans
Alpha 1 antitrypsin is an inhibitor of elastase, enzyme that hydrolyzes elastin,which is produced by neutrophils.
In patients with this defficiency, alveoli are destroyed by elastase which leads to emphysema, exacerbated by smoking which inhibits alpha 1 antitrypsin
Define fibrillin
Glycoprotein which is also secreted by fibroblasts, scaffolds depositions of elastin
Marfans syndrome
1 in 10-20000 births
Autosomal dominant
Mutation of gene encoding for fibrillin
Effects are in ocular, skeletal and cardiovascular systems.
Some people have detached lens and more often arachnodactyly.
glues togethers cells and fibers of the matrix
How does fibronectin play role in wound healing
Becomes incorporated in a clot and attacts fibroblasts and endothelial cells
is an important component of basal membrane
Provides structural support and glues other components of membrane to overlying cells.
Junctional epidermolysis bullosa
Defect in laminin
Blisterin of skin and mucous membranes
Congenital muscular dystrophy
Defect in laminin 2 - links muscle cell to EM
Causes muscle weakness
Proteoglycans are basis for
Ground substance of EM
Proteoglycans are made of
GAG - glycosaminoglycans (mucopolysaccharides) bound to core protein
Carbohydrate is main component and protein is minor
Name 7 forms of GAG's
HEPARIN - in granules of mast cells, liver, lung, skin, anticoagulant
HEPARAN SULFATE- located on cell surfaces and also extracellular, cell communication
HYALURONIC ACID - only non sulphated GAG
Aggrecan is
major proteoglycan of cartilage, interacts strongly with collagen, cotains hylauronic acid, chondroitin sulfate and keratan sulfate
Syndecan and thrombomodulin are
Integral transmembrane proteins, associated with actin cytoskeleton and interactin with fibronectin
Mucopolysacchoridoses are disease associated with
lysosomal storage diseases
Characteristics of mucoplysaccharidoses
Enzyme defficiency is generalized, affecting all organs
Inherited as autosomal recessive or X linked
Can be in both severe and mild forms
Most are not apparent at birht
Defects in degradation of keratan sulfate and dermatan sulfate result in
Skeletal deformities and other CT abnormalities
Defects in heparan sulfate degradation cause
Mental retardation and neurological degeneration
Chondroitin sulfate and hyaluronic acid do not accumulate because
they have alternative passages of degradation
How do you diagnose mucopolysaccaridoses
Presense of GAG's in urine