Cellular Biology I Flashcards
Where is Type II Collagen found?
Cartilage (including hyaline), vitreous body, nucleus pulposus.
What condition is associated with defective type III collagen?
Ehlers-Danlos (p.77)
Where is Type III Collagen found?
Reticulin- skin, blood vessels, uterus, fetal tissue, granulation tissue (p.77)
Where is Type IV Collagen found?
Basement membrane or basal lamina (p.77) Important structural component of basement membrane of kidney, ears, and eyes (p.79)
What condition is associated with defective type IV collagen?
Alport Syndrome (p.77)
What are the major steps in collagen synthesis and where do they occur with respect to the fibroblast?
Steps 1-4 are inside the fibroblast: 1.) Synthesis (RER); 2.) Hydroxylation (ER); 3.) Glycosylation (ER); 4.) Exocytosis. Steps 5-6 occur outside fibroblasts: 5.) proteolytic processing; 6.) cross-linking (p.78)
Describe Step 1 of collagen synthesis.
Synthesis occurs inside the fibroblast in the RER. It involves translation of collagen alpha chains (preprocollagen, usually Gly-X-Y where X and Y are proline or lysine) (p.78)
Describe Step 2 of collagen synthesis.
Hydroxylation occurs inside the fibroblast in the ER. It involves hydroxylation of specific proline and lysine residues and requires vitamin C (p.78)
Describe Step 3 of collagen synthesis.
Glycosylation occurs inside the fibroblast in the ER. It involves glycosylation of pro-alpha-chain hydroxylysine residues and formation of procollagen via hydrogen and disulfide bonds (triple helix of 3 collagen alpha chains) (p.78)
Describe Step 4 of collagen synthesis.
Exocytosis of procollagen (triple helix of alpha chains) into extracellular space (p.78)
Describe Step 5 of collagen synthesis.
Proteolytic processing occurs outside the fibroblast. It involves cleavage of disulfide rich terminal regions of procollagen, transforming it into insoluble tropocollagen (p.78)
Describe Step 6 of collagen synthesis.
Cross-linking occurs outside the fibroblast. It involves reinforcement of many staggered tropocollagen molecules by covalent lysine-hydroxylysine cross-linkage (by Cu2+ containing lysyl oxidase) to make collagen fibrils (p.78)
What condition is associated with problems forming the collagen triple helix?
Osteogenesis Imperfecta (p.78)
What condition is associated with problems in cross linking collagen?
Ehlers-Danlos (p.78)
What is Osteogenesis Imperfecta?
Genetic bone disorder (brittle bone disease). Characterized by multiple fractures with minimal trauma (may occur during birthing process), blue sclerae due to translucency of connective tissue over chordial veins, hearing loss (abnormal middle ear bones), dental imperfections (lack of dentin) (p.78)
