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43 Cards in this Set
- Front
- Back
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1. Components of CT?
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Cells
Collagen Proteoglycans Glycoproteins Salts, nutrients, water **All of these except cells are components of extracellular matrix |
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2. How are the components of CT held together?
Three bond types? |
1. Hydrogen bonds
2. Electrostatic bonds 3. Covalent bonds |
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3. How does collagen most commonly exist?
What does it do? |
As long fibers within tissues
Provides tensile strength |
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4. How do cells interact with the ECM?
What are these? What are the main CAMs? |
Through cell adhesion molecules (CAMs)
Membrane-spanning glycoproteins 1. Cadherins 2. Integrins 3. Selectins 4. Immuniglobulin |
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5. Where do integrins bind to their ligands?
What are their ligands? |
At Arg-Gly-Asp
ECM proteins collagen, laminin, fibronectin |
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6. What is the most abundant protein in the body?
Where is this protein most abundant? Where is it low? What does it have at the beginning? How is it matured? |
Collagen (25% of the proteins)
-in all tissues and organs Abundant in skin Low in liver Has signal sequence in beginning Matured by additional cleavages |
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7. What type of protein is collagen?
How is the structure of collagen? What is tropocollagen? |
Trimeric protein
Three polypeptides ("alpha" chains) are wound together in a fairly rigid helix -very stable and hard to untwist Three-stranded collagen molecule |
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8. Which amino acid is every third amino acid residue of each polypeptide?
What is the amino acid composition of collagen? |
Glycine
1. 33% Gly 2. Proline 3. Hydroxyproline 4. Hydroxlysine |
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9. What does collagen play a role in?
Describe Type I collagen fibril. (two points) |
Structural role in the ECM
1. Most abundant type of collagen 2. Has 2 identical polypeptides from 1 gene and another polypeptide from a different gene |
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10. How are hydroxyproline and hydroxylysine made?
What is the reducing agent for the proline and lysine hydroxylase reactions? |
Post-translational modification of proline and lysine
**modified after incorporation into the chain Ascorbic Acid (vitamin C) |
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11. What does lack of ascorbic acid result in?
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Scurvy (seen first in the mouth)
Decreased bydroxyproline and hydroxylysine in collagen causing instability of the triple helix **Collagen is more rapidly degraded |
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12. How is the tropocollagen in fibrillar collagen?
What type of appearance do microfibrils have? How are tropocollagen molecules organized? |
Tropocollagen triple helical molecules associate in a regular, staggered fashion to form microfibrils
Striped appearance In stepwise arrangement that produces lacunar and overlapping regions |
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13. What stabilizes collagen?
What amino acid is involved? |
Covalent intra- and intermolecular crosslinks
Crosslinks involve lysine side chains (and allysines) |
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14. Where does collagen biosynthesis begin?
What is cleaved in the beginning of collagen biosynthesis? Where does hydroxylation of proline and lysine occur? |
Lumen of rough ER
-synthesis and entry of prepro-alpha chain Signal peptide Lumen of rough ER |
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15. What modifications are made to the in the lumen of the rough ER?
(three things) What leaves the lumen of the rough ER to go to the Golgi? |
1. Addition of N-linked oligosaccharides
2. Addition of galactose 3. Disulfide bond formation Triple-helical procollagen |
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16. What happens in the golgi to the procollagen?
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Addition of sugars (glucose)
More modifications |
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17. Where is the mature tropocollagen formed?
How does this happen? |
In the extracellular space
***leave cell via exocytosis as procollagen Removal of N and C terminal propeptides |
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18. How are collagen fibrils formed?
What are collagen fibers? |
Lateral association of collagen molecules followed by covalent cross linking
Aggregation of fibrils |
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19. How are collagen fibrils and microfibrils arranged in...
1. Tendons 2. Cartilage 3. Sking 4. Cornea |
1. Parallel bundles
2. Assoc w/ GAGS (no distinct microfibril arrangement) 3. Planar sheets of microfibrils layered at many angles 4. Planar sheets stacked crossways for strength |
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20. How is type IV collagen?
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Kinked where the repeat (Gly-X-Y-) is interrupted
Where suppose to have Gly have different AA The kink gives it different properties such as that is forms networks |
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21. Where is elastin found?
What is the AA composition of elastin? |
In all CT but more abundant in tissues that stretch and contract (i.e. aorta, lung, skin)
33% glycine 10-13% proline |
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22. How is elastin arranged?
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Does not have a strict repeating pattern of AA like in collagen
15 random coiled, stretchable hydrophobic regions (gly, pro, val) alternate w/ equal # of regions rich in ala and lys |
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23. How is the appearance of elastin?
Does elastin have crosslinks? What are desmosine? |
Amorphous
Yes, they involve lysine residues to form a crosslinked network Crosslink unique to elastin composed of 4 lysines |
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24. What are glycoproteins?
What is there structure like? |
Proteins carrying carbohydrates
Typically have < 12-15 sugars/attachment sites Sugar structure may be branced Several different sugars/structures Sugars are N or O linked |
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25. What are proteoglycans?
What are GAGS? |
Glycoproteins w/ GAGS
Long, unbranched repeating disaccharide chains May have > 100 sugar residues/attachment site (linear) Sugars are O-linked |
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26. What role do GAGS play?
What proteins are sugars usually on? How do glycolsylation patterns differ? |
Structural (probably do not play a role in folding of associated protein)
Usually on proteins that are secreted or on extracellular portion of membrane proteins Same protein from different tissues can have different glycosylation patterns |
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27. What are the 5 main types of repeating disaccharides in GAGS?
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1. Chondroitin Sulfate
2. Keratan Sulfate 3. Heparin; Heparan Sulfate 4. Dermatan Sulfate 5. Hyaluronate |
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28. What do most consist of?
How are most modified? |
Uronic acid (glucuronic or iduronic acid( and amino sugar
**exception is keratin sulfate which has galactose Modified by sulfation |
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29. What is chondroitin sulfate similar to?
How is it different though? |
Dermatan sulfate
Chondroitin: glucuroninc acid Dermatan: Iduronic acid |
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30. Where is heparin found?
What is unique to heparin? |
In mast cells (intracellular)
More heavily sulfated than the others |
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31. What is special about hyaluronate?
(two things..) Where is it present? |
1. Not sulfated
2. Not covalently attached to proteins Present in ECM |
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32. How do the locations of heparin and heparan sulfate differ?
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Heparan Sulfate
-Found on proteins of ECM (extracellular) Heparin -In mast cells (intracellular) |
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33. How is a GAG linked to a proteoglycan molecule?
What is being linked? |
Through a specific "link trisaccharide"
Linkage is between GAG chain and a serine residue of a core protein in a proteoglycan |
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34. How are sugar chains built up?
How is the sugar to be added activated? Why are nucleotide sugars important? |
One residue at a time
Couple w/ a nucleotide (usu UDP) Nucleotide sugars are substrates fro glycosyl transferases |
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35. What do glycosyl transferases do?
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Catalyze sugar addition
**many different glycosyl transferases that are specific |
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36. How are sugars usually attached?
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Attached to proteins through....
1. O of serine or threonine ("O-linked") 2. N of asparagine ("N-linked") |
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37. How are proteoglycans synthesized?
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1. Synthesize protein
2. Attach carb residue one at a time to form GAG 3. Modify sugars in chain |
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38. Where does sugar modification occur?
What does it depend on? |
ER or golgi
Availability of transferase and substrate |
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39. What are 6 functions of proteoglycans?
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1. Lubrication
2. Gel formation 3. Cement 4. Ion binding 5. Molecular sieves (kidney) 6. Shock absorber |
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40. What are mucins?
What are their properties similar to? |
High-molecular weight glycoporteins
Have properties of proteoglycans but are not (sugar chains are not GAGS) |
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41. What are the functions of mucins?
What types of mucins are there? (three) |
Lubrication and protection of gastrointestinal, respiratory, and genital tracts from physical damage, dehydration, and bacterial infection
1. Gel-forming 2. Soluble 3. Membrane-bound |
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42. What is the structure of mucins?
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1. Several thousand AAs long
2. Central region w/ short AA sequences -rich in serines and threonine |
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43. What is the configuration of the polypeptide and why?
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Extended or unfolded
B/c there is a high frequency of short sugar chains |
