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63 Cards in this Set
- Front
- Back
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Which part of an IF is conserved, and which is not?
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The core is conserved, and the amino and carboxyl ends are not.
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How do IF proteins associate to form IFs?
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Side by side and end to end. 8 tetramers twisted together makes a ropelike IF. The tetramers are held together by noncovalent bonds.
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In an IF filament, what shape characterizes the central rod?
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Alpha helix.
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In an IF filament, how do monomers associate?
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They wrap around each other to form a dimer.
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In an IF filament, how do tetramers form?
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Two dimers of opposite polarity associate in a staggered way. Noncovalent bonds occur between the dimers.
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Which type of filament helps determine the shape of many cells?
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IFs.
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What does plectin do in the cytoskeleton?
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It cross links IFs to each other, to actin, and to MTs.
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How does ALS occur?
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Abnormal IFs (neurofilaments) damage axons.
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How does desmin-related myopathy occur?
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Desmin, a muscle IF, is damaged and disorganized.
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How does epidermolysis bullosa simplex occur?
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Defective IFs (keratin) in skin cause blisters.
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What is progeria?
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Disease caused by defective nuclear lamins (IFs); causes premature aging in children.
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What's the general structure of MTs?
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Their walls consist of 13 protofilaments comprised of 4 nm by 8 nm long heterodimers. Each heterodimer consists of an a-tubulin and a b-tubulin molecule. These molecules appear in about all eukaryotes. MTs lengthen and shorten by adding and subtracting their heterodimers. Whole MT is 24nm in diameter.
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Where would you find long-lived MTs?
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Cilia.
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Where would you find the most dynamic MTs?
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Mitotic spindle.
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Name two drugs that depolymerize MTs.
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Vinblastine and vincristine.
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Where does MT nucleation occur?
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Centrosomes AKA MTOCs.
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On MTs, which way does dynein move?
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Usually toward the minus ends.
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On MTs, which way does kinesin move?
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Usually toward the plus ends.
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When (in the cell cycle) do controsomes nucleate MTs?
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Interphase.
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Where in the migrating cell does the MTOC appear?
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To the anterior end.
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Since there is constant dis/ass of MTs, how much of the tubulin dimers are assembled or in a pool of dimers at any given time?
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About 50/50.
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Which drugs bind to tubulin dimers, causing disassembly?
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Vincristine (child leukemia), vinblastine (child leukemia), and colchinine (treats gout).
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What drug binds to MTs and causes rapid assembly?
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Taxol--a cancer drug that inhibits mitosis. MTs are too excessive to function.
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How are actin filaments formed?
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F-actin is formed by polymerization of G-actin monomers. Two protofilaments with the same polarity bind around each other tightly to form a 7nm diameter right-handed helix which repeats its structure every 37 nm.
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Is F-actin polar?
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Oh, yes.
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Where does nucleation of F-actin occur?
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At the ARP complex--a site with two actin related proteins.
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How does Listeria make its way through its host?
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It polymerizes G-actin to F-actin to propel itself through its host's cytoplasm.
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What role does F-actin play in microvilli and stereocilia?
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Support. Actin in these projections are bound laterally to each other.
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What are the actin binding proteins?
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Gelsolin, which fragments actin filaments; Filamin, which cross-links actin filaments to form a gel; and Fimbrin, which bundles actin filaments together.
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Which way does myosin move on actin filaments?
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To the + end, with one exception (myosin 14)?
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What cytoskeletal element is used in cytokinesis?
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Actin.
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What's the energy source used in actin assembly/disassembly?
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ATP, yo.
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How many different actin binding proteins are there?
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Lots. Most cells contain over 100.
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What does thymosin do?
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It's a monomer-sequestering protein that holds monomers so that they can't assemble. This prevents excessive polymerization of actin monomers.
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How many different myosin molecule types are there?
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Over 30.
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Which myosin moves vesicles along actin?
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Myosin-I. It has one head and one tail.
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Which myosin is involved in muscle contraction?
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Myosin-II. Has two heads and a tail.
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What are the motor molecules on MTs?
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Kinesin and dynein.
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Kinesin is pretty similar to ____.
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Myosin.
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Which part of motor molecules enables them to recognize and move specific cargo?
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The tail. There are different types of tail depending on the cargo carried.
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How fast can vesicles and mitochondria move?
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5 microns/sec.
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How big are kinesin's "steps"?
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8nm. Same as the length of one tubulin heterodimer. Each step requires hydrolysis of one ATP.
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What is Charcot-Marie-Tooth (CMT) neuropathy?
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Mutation of a kinesin found in axons. Transport of precursors for synaptic transmission is interrupted--leading to axonal degeneration.
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What is retinitis pigmentosa?
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Caused by a defect in a kinesin affecting transport in retinal cells.
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Mutation in which myosin causes deafness?
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Myosin VI.
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How does lidocaine work?
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Inhibits kinesin movement in axons--stops anterograde transport of neurotransmitters.
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What virus uses kinesin to move along MTs?
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Herpes!
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MTs consist of strands of:
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Protofilaments.
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Actin consists of strands of:
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F-actin.
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IFs consist of strands of:
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8 tetramers.
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The basic monomer of MTs is:
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alpha/beta tubulin heterodimer.
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The basic monomer of actin is:
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G-actin.
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What are metachronal waves in cilia?
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Describes a type of beating where each cilia is slightly out of phase with its neighbor.
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How do cilia bend?
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Nexin and radial links (spokes) hold two MTs together; what would be sliding becomes bending.
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What motor molecule is used in cilia?
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Dynein. There are two dynein arms, an outer and an inner.
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What causes immotile cilia syndrome?
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Lack of inner and outer dynein arms.
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What's the sliding doublet model?
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Describes how ATP causes conformational changes in dynein arms in cilia which cause a doublet to walk along its neighbor. This can't go too far because of the radial spokes and nexin. Therefore, the the sliding is converted into bending.
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What are symptoms of immotile cilia syndrome?
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Cannot clear mucus with inhaled particles from their respiratory epithelia...leads to recurrent lung infections.
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In cilia, how do you distinguish between subdoublets?
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A has 13 protofilaments; B has 10 protofilaments. B is farthest from the centriole pair.
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What happens at the basal body of a flagellum?
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There is no center MT anymore (9+0 structure). This is called a centriole or a basal body. At the centriole, each of the 9 MTs now has triplets instead of doublets. The triplets have 13, 10, and 10 protofilaments.
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Do primary cilia have dynein?
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No. They don't move.
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What might be a function of primary cilia?
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Some have signaling proteins and appear to be important in development. i.e. in fibroblasts, bone cells, and neurons. In kidney tubules, they serve as flow sensors to monitor fluid mvmt.
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How is polycystic kidney disease caused?
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Defects in primary cilium lead to a failure in monitoring fluid flow--overproduction of kidney cells leads to kidney failure.
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