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67 Cards in this Set
- Front
- Back
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cell-cell adhesion
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actin filaments
IF tight junctions (claudins) adhesion belt (cadherins) desmosome (cadherins) gap junction (connexins) |
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Cell-matrix adhesion
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hemidesmosome (integrins)
focal adhesion (integrins) integral membrane proteoglycan |
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Connective tissue
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epithelium, basal lamina, fibroblast, collagen fiber, capillary, mast cell, elastic fiber
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ECM is made and oriented by the cells within it
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made of proteins and oligosaccarides
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ECM has 2 main classes
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glycosominoglycans (GAGs)
Fibrous proteins |
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GAGs are
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polysaccharide chains covalently linked to protein (proteoglycan), highly hydrated.
-function: resists compression |
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fibrous proteins
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collagen, elastin, fibronetin, laminin
function: structural adhesive |
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collagen is a fibrous protein that
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offers strength, organization, resistance to proteases
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elastin is a fibrous protein that
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resilience (rubberlike). recoil ability (spring)
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fibroblast is the
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predominant cell type; are secreting part of the ECM
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ECM functions
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stabilizes tissues, regulates behavior of cells that contact it, influence their survival, development, migration, proliferation, shape, and function
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ECM is highly?
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highly hydrated, sugar chains tend to suck in water surrounded by them, pillow out or resist compression
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cornea
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hydrated gel removed
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fibroblasts secrete
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in most connective tissues, the matrix molecules are secreted by fibroblasts
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how do you resist compression?
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the ability to recruit or bring in molecules of water to resist compression
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collagen
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give strength and organization while helping resist proteases (physically push things away from the cell)
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elastin
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the ability to push back
when you get older, you get wrinkles because you cannot recoil or spring back |
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proteoglycan
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sugars (more) modified with protein (attached covalently)
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what happens when you remove hydrated gel
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you see fibrous proteins that are highly enriched and highly branched
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GAGs occupy
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large amounts of spcae and form hydrated gels
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what are the 4 types of GAGs
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hyaluronan
chondroitin/dermatin sulfate heparan sulfate keratin sulfate |
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GAGs are differentiated by
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sugar composition, linkage types, #, and location of sulfates
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repeating disaccharide contains two sugars
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uronic sugar and amino sugar (usually sulfated)
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Sugars =
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GAGs
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GAGs are one of the next ____ molecules
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anionic
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repeating disaccharide is between
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70-200 sugars long
high density of negative charges contributed to by uronic sugar and sulfate molecules |
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GAGs adopt highly
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extended conformations
-withstand compressive forces -provide mechanical strength -high volume to mass ratio |
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the space that hyaluronan takes up also should include
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clouds of water (suck in clouds of water) thus takes up huge space
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GAGs adopt highly extended conformations because
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stiff
strongly hydrophilic forms gel even at low conc. |
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most abundant biopolymers on earth
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chitin and cellulose (insect and plant polysaccharides)
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hyaluronic acid
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very long polyanion, forms hydrated gels
major component of matrix surrounding migrating and proliferating cells imparts stiffness and resiliency, lubrication to connective tissues repeated disaccharide unit of glucuronic acid |
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hyaluronic acid continued
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simplest and not typical of majority of GAGs
lacking sulfates, still highly anionic thus form hydrated gels |
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how do you form hydrated gels?
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must be highly anionic or negatively charged
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proteoglycans are composed of?
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GAG chains covalently linked to a core protein
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functions of proteoglycan
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act as a molecule sieve (because it is highly branched) similar to electrophoresis
-chemical signaling -bind and regulate secreted proteins (i.e. proteases) |
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proteoglycans can regulate the
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activities of secreted proteins
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regulation of protein activity by proteoglycans
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immobolize protein near site of synthesis or sterically block activity
-provide reservoir or protein by delayed release -protect protein from proteolytic degradation and thus prolong its activity -alter or concentrate a protein for more effective presentation to cell surface receptors |
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collagen
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major protein of ECM
3 polypeptide strands wound together into an alpha-helix make up 1/3 feeling "stiff" because old people lose collagen |
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collagen usually gly-x-y
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x and y are any amino acid
but x is usually proline and y is commonly hydroproline |
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proline is helpful for
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stabilizing helix because of its ring structure
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proline
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stabilizes helix
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glycine
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small so allows tight packing
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collagen fibrils first made in
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inactive form (made in pro-alpha chain in ribosomes and secreted into ER
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forming collagen fibrils
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synthesis of Pro-alpha chain
hydroxylation of selected prolines and lysines glycosylation of selected hydroxylysines self-assembly of 3 pro-alpha chains procollagen triple helix-formation -secretion |
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1st step in forming collagen
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synthesis of pro-alpha chain
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2nd step in fc
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hydroxylation of selected prolines and lysines
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3rd step in fc
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glycosylation of selected hydroxylysines
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4th step in fc
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self-assembly of 3 pro-alpha chains
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5th step in fc
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procollagen triple helix formation
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6th step in fc
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secretion
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forming collagen step 7
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cleavage of propeptides
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8th step in forming collagen
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self-assembly into fibril
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9th step in fc
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aggregation of collagen fibrils to form a collagen fiber
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when do you have a mature collagen molecule?
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when proteases cleave off propeptides
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the underlying cortical cytoskeleton influences fibril assembly
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sites
rates (of assembly) orientation |
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cross-linking
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modified amino acids common in collagen
-formed by enzymes after incorporation into procollagen molecules -covalent intramolecular and intermolecular cross-links are formed btw modified lysin side chains within a collagen fibril |
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covalent cross-linking occurs btween lysines molcules and types of covalent bonds are found only in
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collagen and elastin
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elastin
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composed of 2 types of short segments
-highly hydrophobic segments (pro,gly) -alpha-helix segments (ala,lys) |
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elastin functions
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elasticity
collagen is the counter balance to elastin |
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multiadhesive matrix proteins
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link cells to various matrix components
-link together various matrix components -organize the matrix -regulate cell attachment to matrix -regulate cell migration and shape |
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types of mulitadhesive matrix proteins
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laminin
fibronectin entactin thrombospondin vitronectin chondronectin |
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fibronectin dimer has 2 different forms and promotes
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it is soluble and fibrillar
type 3 fibronectin repeat -main module, binds integrins via RGD 90 a long promotes cell attachment to matrix promotes cell migration |
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3 ways in which basal laminae are organized
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muscle, epithelial, kidney glomerules
-specialized ECM -found at interface btw cells and connective tissue -found in some specialized tissues |
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basal lamina
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basement membrane
-fibrous content: -structure type IV collagen adhesion proteins: laminin and enactin |
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basal lamina
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sheetlike network of ECM
underlying basal surface of epithelial and endothelial cells |
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basal lamina resembles a mat and serves to
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filter molecules
organize cell surface molecules organize epithelia into sheets define migration pathways cell polarity |
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integrins
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adhesion receptors
bind Arg-gly-asp-ser |
