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21 Cards in this Set
- Front
- Back
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What is the most abundant protein in the human body, its main function, and about how much is in a typical person?
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Collagen
Main fnxn - maintain shape & resisnt deformation of tissues 13 lbs of collagen in 150 lb person |
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What are the general amino acid composition characteristics of collagen?
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Glycine - 33%
Proline - 10% Hydroxyproline - 10% Hydroxylysine - 1% 60% sequence - Gly-Pro-X / Gly-X-Hyp 40% sequence - various sequences w/ every 3rd being glycine Each alpha chain - L-handed helix w/ 3 amino acids per turn |
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Pre-pro-collagen
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Initial form of collagen which has its "signal peptides" cleaved off by signal peptides
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Procollagen
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One of the forms of collagen in its synthesis. N and C terminus peptides removed from procollagen to form tropocollagen
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Tropocollagen
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Basic structural unit that is made of 3 polypeptide alpha chains w/ 1050 a.a. in each
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Describe 4 modifications that take place to procollagen. Which requires vitamin C?
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Hydroxylation (requires vitC)
Glycosylation N-linked glycosylation Formation of disulfide bonds Formation of triple helix O-linked glycosylation |
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Describe hydroxylation of procollagen
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Subset of proline & lysine resides in region where triple helix formation occurs is hydroxylated by lysyl hydroxylase by 2 prolyl hydroxylases
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Describe glycosylation of procollagen
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Galactose from UDP-gal is added to specific hydroxylysyl resides by galactose tranferase
Glucose from UDP-glucose - added - glucose transferase |
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N-linked glycosylation of procollagen
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takes place on certain asparagines on C-terminal end of peptide
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Formation of disulfide bonds of procollagen
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oxydatiion of certain cysteines to form interchain S-S links in pro-peptides
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Describe formation of triple helix in procollagen
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formed b/w alpha chains, and pro-peptides are then transported to golgi body
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Describe O-linked glycosylation in procollagen
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Takes place and pro-collagen is packaged into transport vesicles for export
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What is elastin, its color, and what is its function?
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-2nd most major protein of connective tissue
-Yellow insoluble protein -Predominant protein of elastic structures such as walls of large blood vessels |
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What are the similarities and differences b/w amino acid composition of elastin and collagen?
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Like collagen - about 1/3 of the a.a.'s are glycine
But, valine/alanine content are higher (13% & 23%) while proline/hydroxyproline are about 10% |
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What enzyme modifies lysines to a form, which will eventually cause cross-linking to occur in collagen and in elastin?
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Lysyl oxidase (produces allysine)
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What are the structures in elastin crosslinks called?
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Desmosine (isodesmosine)
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What general composition characteristic of proteoglycans makes them dramatically different from collagen or elastin?
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Have a core protein and glycosaminoglycans; the polysaccharadie content is very high => up to 95% by weight
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What 3 general characteristics do proteoglycans have in common?
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1. repeating disaccharide units in which D-glucosamine or D-galactosamine are present
2. All except keratan sulfate contain a uronic acid 3. Ester sulfate groups are in all except hyaluronic acid |
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Name 4 different proteoglycans and give their approximate molecular weight
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hyaluronic acid: 4 to 8 E6
Chondroitin sulfate: .5 to 5 E4 Dermatan sulfate: 1.5 to 4 E4 Heparin,Heparan sulfate: 1 E4 to over 1 E6 |
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What are the 2 different types of fibronectins, and what functions do they perform?
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Insoluble (in extracellular matrix) and soluble (in plasma & other fluids)
Plays a major role in adhesion of cells to one another and to surfaces. Helps maintain cell morphology |
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What are the structural features of fibronectin, and to what does each domain bind?
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2 chains of similar size and structures joined near carboxy terminal ends by disulfide linkage
- each chain has 3 domains: --32kD domain near carboxy terminus binds: glycosaminoglycans --40kD domain w/ oligosaccharide side chains binds: collagen --140-150kD domain binds: both cell surfaces as well as glycosaminoglycans |
