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39 Cards in this Set
- Front
- Back
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What makes up the cytoskeleton?
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It is made up of 3 different systems. Microfilaments, intermediate filaments, and microtubules.
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What are the sizes of the the cytoskeleton components?
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Microfilaments - 5nm
Intermediate filaments - 10nm Microtubules - 25nm |
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What are microfilaments?
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polymers of actin. It is a globular unit. It suports cell membranes or bundle to resist tensile forces. 5nm
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What are intermediate filaments?
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Various cell or tissue-specific proteins. It is a filamentous. It resists tensile forces via cell junctions. 10nm
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What are microtubules
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A tubular complex of repeated tubulin monomers. Globular protein.Resists shear forces and has the ability to do work.
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What cytoskeleton component has the ability to do work?
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microtubules
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Is the cytoskeleton rigid or flexible?
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The cytoskeleton is a flexible and dynamic network of filmanets.
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What is the role of microtubules in cellular function and disease?
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It determines cell shape and polarity of all cells. Intracellular transport. Cell movement and ciliary movement. Cell division
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How does generic polymer vary in function in a cytoskeleton?
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Associated proteins!
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Rank the possible interactions between cytoskeleton subunits
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IMF>MT>MF
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Why do microfilaments bundle?
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For strength. Their resistance to tensile forces is weak. They crosslink to make stronger
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What form are MF, MT, and IMF in the cell at equilibrium?
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MF and MT are 50:50 monomer:polymer
IMF is mostly polymer |
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What are some MT related clinical issues?
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Cell shape/polarity
Intracellular transport Cell movement Cell division |
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Are microtubules polar?
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Yes
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How are microtubules organized?
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Dimers align head-to-tail forming protofilaments. Protofilaments align (13) into microtubule.
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What is the (+) end of a microtubule?
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the Beta end
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Which side of a microtubule assembles/disassembles faster?
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the (+) beta end is faster
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What is a microtubule organizing center (MTOC)?
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It is a centrosome. The negative end of the microtubule is at the centrosome
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How does GDP and GTP change microtubules?
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When GTP bound, tubulin is straight. When GDP bound, it is bent and not stabile. Average half-life is 10 minutes
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What is the most critical factor in growing the length of microtubules?
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GTP tubulin
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Neuronal microtubule
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Special type.
Axom - (+) end away from cell Dendrite (mixed polarity) |
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How stable is the cytoplasmic MT, mitotic spindle, Neuronal MT, axonemal MT, and centrioles/basal bodies?
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--Cytoplasmic - 10 minutes. More resistant to depolymerization
-- Mitotic spindle - very dynamic. 15 seconds unless capped -- Neuronal - partial -- axonemal -- stabilized centriole/basal - stabilized |
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What is a MT doublet?
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One complete MT with 9 protofilaments around it. arranged circularly. Ex is cilia and flagellum
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What is a MT triplet?
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centrioles and basal bodies
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What modifies the stability of microtubules?
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Post-translational modification tubulin.
-phosphorylation, acetylation... microtubule associated proteins (MAPs) |
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What is a microtubule associated protein (MAP)?
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binds to MT to increase stability. Some possess ""arm" domain. Higher molecular weight - MAP 1,2,3,4,5. Lower molecular weight Tau. Motor proteins can be MAPs.
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What regulates MAPs?
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Developmental - transient expression
Spatial - Tau in axon only, MAP2 in cell body and dendrites Phosphorylation - decreases affinity of MAPs for MT. |
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What does hyperphosphorylation of tau in Alzheimers do?
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It reduces axonal MT stability. Transport is reduced.
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What is stathmin
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curved MAP that prevents assembly of tubulin
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What is Kinesin-13?
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Rips tubulin from ends of MT
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What is Katanin?
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It severs MT
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What are TIPs
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Caps MT and makes them stable. Attaches them to membranes/chromosomes
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What does Colchicin do to MT?
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It binds to tubulin dimer, adds to polymer and blocks further addition. Disassembly can occur. Net result = disassembly
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Vinca Alkaloids
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Precipitates tubulin, pulls them out so equilibrium is changed and therefore less tubulin.
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What does Taxol do?
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It hyperstabilizes MT
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What does chemotherapy target for MT?
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It targets dynamic MT. Detrimental to blood cell production, GI tract lining, neuronal transport
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What are kinesins?
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They are motor proteins with a globular head for MT binding and ATPase activity. Has filamentous shaft. tail carries cargo. Most are dimeric. Most go towards (+) end
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What are Dyneins
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Minus end directed transport proteins. Globular heads, Short shafts. Two types: Cytoplasmic and axonemal dynein.
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Which way do kinesin and dynein move?
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Kinesin - outwards
Dynein - inwards |
