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68 Cards in this Set
- Front
- Back
- 3rd side (hint)
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what are the functions of the cytoskeleton?
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-maintain stability in cytosol
-maintian shape -internal cellular movement -external cellular movement |
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Protein filaments of the cytoskeleton interact with what other kinds of proteins? What are their functions?
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-accessory proteins (controlled assembly of filaments)
-motor proteins (movement of organelles or filaments) |
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Describe actin
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-flexible
-found along periphery of cell under plasma membrane -made of monomers --> polymer strands --> helix -can be arranged in 3 dimensions (gives cell plasticity) -cell surface organization |
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Describe microtubules
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-long, rigid, straight tubes
-monomers are aB heterodimers; 9 of these protofilaments make a tube-->MT -cell highway -MTOC at exact center of cell (-) and (+) goes to periphery of cell -polar |
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Describe intermediate filaments
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-heterogeneous family
-ropelike structure, tetrameric -goes from cytoplasm of 1 cell to another cell (junction) -tissue stability -no polarity -not ATP or GTP dependpent for polymerization (phosphorylation) -flexible |
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How are actin and MT dynamic during mitosis?
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-centrosomes move to opposite ends, MT emanate from them (forming cytoskeleton of 2 daughter cells)
-actin concentrates in the middle and divides the cell into 2 cells (constriction ring) |
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Describe the polarity of MT
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-(+) beta end is active (toward periphery)
-(-) alpha end is more inert (towards center, stabilized at MTOC) -individual MT at MTOC are changing length independently of each other |
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Describe a centrosome
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-pair of centrioles at right angles to each other
-pericentriolar matrix has gamma-tubulin ring complexes (nucleases) keep MT ends in centrosome |
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What is the structural difference between growing and shrinking MT?
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-growing MT has GTP cap
-GTP bound to monomers; as monomers are added, added so quickly that there's no time to hydrolyze GTP so the protofilament keeps growing |
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compare the stability of (+) and (-) ends of MT
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-both are equally unstable
-(+) ends have capping proteins at periphery or wherever target is |
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What molecules are involved in the stabilization of MT?
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-capping proteins stabilize (+) ends
-MT associated proteins (MAPs) stabilize MT during tubulin polymerization |
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What do catastrophins do?
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destabilization of MT
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What are the 2 types of stable MT?
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-MTOC (centrosomes in center, basal bodies of cilia and flagella towards periphery)
-axoneme (motile core of cilia and flagella) |
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Describe axoneme and give examples
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-motile structures built from MT and dyenins
-eg. cilia and flagella (9 doublets+2central singlets) -basal body gives rise to cilia and flagella nad has 9 triplets and 0 central singlets |
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Describe the MT structure of cilia
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-9 peripheral doublets, 2 central singlets
-Dynein arm between doublets and attaches to neighboring MT to allow movement |
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Motor proteins bind to which 2 cytoskeletal filaments? Why?
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-actin and microtubule
-binds only to polarized filaments |
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What are the 2 MT motor proteins and in which direction do they move?
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-Kinesin: moves toward (+)
-Dynein: moves toward (-) -both have globular heads that bind to MT, tails that carry cargo |
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If Golgi wants to go towards the center of the cell, which motor protein would it use?
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dynein
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If ER wants to move toward the periphery of the cell, which motor protein would be used?
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kinesin
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What are the functions of MT?
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-organize the cell (centrosome)
-form mitotic spindle -Provide highways for organelle transport (internal movement) -cell motility (external movement) |
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Describe the structure of actin
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-G-actin monomers make F-actin polymers, which makes a double helix
-Uses ATP in polymerization (end with ATP is growing end) -Polar (+ and - ends) |
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What is a classic example to understand function of actin?
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locomotion of lamellipodium
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Describe function of fibrin, spectrin, and alpha actinin in lamellipodium
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-fibrin: keep bundles straight
-spectrin: gel-like network -alpha actinin: contraction |
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Describe actin organization
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- (-) end in nucleating organizing center positioned towards periphery of cell
-capping proteins to stabilize and give direction to polymerizing end |
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What is the capping protein of actin?
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-formin dimer
-gives stability to (+) end -gives growth direction of actin |
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Compare and contrast the 2 cross linking proteins alpha actinin and fimbrin
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-both bind to actin, but have different function in movement
-alpha actinin is involved in contraction; gives a lot of space between actin filaments so that myosin-II can come in and perform contractile element -fimbrin is involved in protrusion function; gives less space between actin so no room for myosin-II to come in |
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Which cytoskeletal filament gives support to microvilli and what are the cross linking proteins involved?
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-actin
-villin and myosin-I |
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What kind of anchoring junction is actin involved in? How does it form the junction?
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-zonula adherens
-makes the tube between the cells |
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what is the motor protein that functions with actin?
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-myosin II (muscle contractions)
-2 globular heads that bind to actin filament |
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What are the functions of actin filaments?
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-external cell shape
-cell motility -microvilli formation -muscle contraction -development of tubes -cell polarity -cleavage furrow in dividing cells -participate in anchoring junctions |
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What are the functions of intermediate filaments?
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-tissue stability (spans across one cytoplasm to another cell cytoplasm)
-support nuclear envelope (lamins) -participate in anchoring junctions (cell-cell, cell-matrix) |
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what is the accessory protein that works with intermediate filaments?
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Plectin
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What are the 4 classes of intermediate filaments?
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-Keratins (epithelia)
-Vimentin-like (astrocytes-GFAP, muscle cells-desmin, msenchymal cells-vimentin) -Neurofilaments (neurons) -Lamins (nuclear laminae) |
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Why are drugs and toxins that affect the cytoskeleton bad?
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affects dynamic characteristic of the filaments
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What are 2 disease processes that can affect the cytoskeleton? Which is more common?
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-genetic deffects
-cell injury (more common) |
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what are the 3 classes of cell junctions?
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-occluding
-anchoring -communicating |
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what is the accessory protein that works with intermediate filaments?
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Plectin
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What are the 4 classes of intermediate filaments?
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-Keratins (epithelia)
-Vimentin-like (astrocytes-GFAP, muscle cells-desmin, msenchymal cells-vimentin) -Neurofilaments (neurons) -Lamins (nuclear laminae) |
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Why are drugs and toxins that affect the cytoskeleton bad?
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affects dynamic characteristic of the filaments
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What are 2 disease processes that can affect the cytoskeleton? Which is more common?
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-genetic deffects
-cell injury (more common) |
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what are the 3 classes of cell junctions? Give an example of each.
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-occluding
-anchoring -communicating |
-occluding: tight
-anchoring: desmosomes, hemidesmosomes, adherens (actin, others are IF) -communicating: gap junctions |
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Describe tight/zonula occludens junctions. Name proteins involved in tight junctions
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-outer leaflet of plasma membrane fuse together all around apical perimeter of cells to make sure lumen material doesn't get into between cells
-usually at the top of cell |
-claudin
-occludin |
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Briefly describe anchoring junctions
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links cytoplasm of one cell to other cells and ECM; can be associated with actin or IF
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Describe anchoring junctions that involve actin. List proteins that are involved.
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-cell-cell: zonula adherens; forms adhesion belt at junction
-cell-matrix: focal contacts/adhesions, more dynamic than zonula adherens |
-zonula adherens: cadherins between cells
-anchor proteins (catenins): link cadherins to actin ends -actin: attaches to anchor proteins at end -cell-matrix: integrins in membrane bind to sticky fibronectin in ECM and achoring proteins attached to actin |
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Describe anchoring junctions that involve intermediate filaments. List proteins involved.
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-cell-cell: desmosomes (macula adherens)
-cell-matrix: hemidesmosomes |
-desmosomes: cadherins between cells; plak anchoring proteins; link to IF at loop
-hemidesmosomes: keratin (skin) end binds to plectin (anchoring protein) which binds to integrin which links the cell to ECM; more permanent than cell-cell adhesion |
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What is Pemphigus vulgaris? Bullous pemphigoid?
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-autoantibodies attack cadherins so destroy cell-cell adhesion
-results in blistering because cells detached |
-antibodies against proteins of hemidesmosomes so epidermis detached from dermis
-results in blistering |
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What are the proteins involved in gap junctions?
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-connexins (6 make a connexon, 2 needed for each gap junction)
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what conditions are needed to close gap junctions?
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-high Ca, low pH-->cell is dying so close junction to prevent spread to other cells
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What are glycosaminoglycans (GAGs)?
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-long, unbranched polysaccharide chains composed of repeating disaccharide units
-1 of the 2 sugars is always an amino sugar, usually sulfated -EXCEPT HYALURONIC ACID |
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Which GAG stands out from the others? Why?
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-hyaluronic acid
-not sulfated |
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What are the 4 main groups of GAGs? Which is the most common?
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-hyaluronan (most common, almost everywhere)
-chondroitin and dermatan sulfate -heparan sulfate -keratan sulfate |
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What are the proteins involved in gap junctions?
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-connexins (6 make a connexon, 2 needed for each gap junction)
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what conditions are needed to close gap junctions?
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-high Ca, low pH-->cell is dying so close junction to prevent spread to other cells
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What are glycosaminoglycans (GAGs)?
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-long, unbranched polysaccharide chains composed of repeating disaccharide units
-1 of the 2 sugars is always an amino sugar, usually sulfated -EXCEPT HYALURONIC ACID |
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Which GAG stands out from the others? Why?
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-hyaluronic acid
-not sulfated, not attached to core protein |
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What are the 4 main groups of GAGs? Which is the most common?
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-hyaluronan (most common, almost everywhere)
-chondroitin and dermatan sulfate -heparan sulfate -keratan sulfate |
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what is a proteoglycan molecule?
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GAG attached to core protein (all GAGs attach to core protein except hyaluran)
-aggrecan is a common example -can attach to hyaluronic acid to make a big aggregate -functions as a selective sieve in basal laminae |
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what is the most common protein in ECM?
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-collagen
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What are the 3 main types of collagen?
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-fibrillar
-non-fibrillar -network forming (IV is common in disease) |
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What proteins are present to keep collagen in place and to organize them?
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fibril
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What type of collagen is most common over all? Which is most common in diseases?
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-overall: fibrillar
-diseases: network-forming |
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What is dermatitis herpetiformis?
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antibodies against anchoring fibrils
-results in blisters (epidermis detaches from dermis) |
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Disease associated with what protein causes scurvy?
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collagen
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Collagen and elastin are both rich in which amino acids?
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-glycine and proline (but elastin is not glycosylated like collagen)
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Marfan syndrome is a disease related to which ECM protein?
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elastin
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What are 2 adhesive glycoproteins found in the ECM?
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-fibronectins
-laminins |
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What are the 2 most abundant proteins found in basal lamina?
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-laminin
-collagen IV |
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Alport's syndrome and Goodpasture's syndrome are disease associated with which part of the ECM? How are they caused
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-basal lamina
-missing collagen IV, antibodies against collagen IV |
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