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28 Cards in this Set
- Front
- Back
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What are the three types of cytoskeletal elements?
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1. microfilaments (smallest 7-9nm) 2. intermediate filaments (middle size 10nm) 3. microtubules (largest 25nm)
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What is the molecular structure of microfilaments?
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G-Actin (monomer) polymerizes to form F-actin (filament) which is ATP dependent (hydrolysis) and binds to G-actin
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Explain how microfilaments are assembled and disassembled.
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A constant assemble-disassemble phase where at the + end G-actin adds to the F-actin by adding ATP and G-actin disassembles a the (-) end when ADP is released. This is called treadmilling.
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Describe how actin binding proteins alter structure and function of microfilaments.
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Necessary for the stabilization of actin and controls polymerization of sites and helps with severing to depolymerize. Ex. Arp2/3-faciliates a cut and a branching in different direction ex. Microfilament bundles are stablized close to gether or in dispersed array lik microvilli are cross-linked by Fimbrin and Villin and stress fibers are cross-linked by α-Actinin ex. actin network that supports cell membrane by Filamin like pseudopodia for phagocytosis or lamellipodia for cell movement
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How are microfilaments organized?
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1. branching of F-actin 2. microfilament bundles which are formed by cross-linking F-actin (ex: microvilli-cross link of F-actin and villin 3.microfilament network- filamin cross-linking actin ex) pseudopodia, lamellipodia
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What type of microfilament organization allows for group cell communication?
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Microvilli, cell cortex (structural support for membrane inside cell), adherens belt (allows cell communication by getting contractions of sheets of cells),
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What type of microfilament organization is important for mitosis and cytokinesis?
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Contractile ring (used during telophase of mitosis to cleave cell into 2 cells
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What is myosin and its basic activity ?
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A motor protein that specifically binds to actin to generate force and movement by "walking" along the actin polymers
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What is the general structure of myosin?
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Myosin chains are formed from 3 domains: 1. Motor head=ATPase activity 2.Neck (lever)=binds to MLCs or calmodulin 3.Tail (rod) helical domain that has diverse function and length
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How do light chains regulate activity?
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in neck region-regulates function and has 2 types: 1. essential light chains 2. regulatory light chains and calmodulin
Sense changes in second messenger activity inside the cell (ex of messenger is Ca++ and it reacts with Calmodulin to form a complex which activates Myosin light chain kinase (phosphoralates of light chain from ATP). This increase motor activity and helps assemble rod like domainsinto bipolar filaments and slide tails to contract cells) |
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How are cellular forces on the inside of the cell through myosin transferred on the outside?
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Stress fibers link to cell surface receptors through anchoring proteins
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Where is myosin II found?
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In Sacromeres in skeletal or cardiac muscle, smooth muscle, and non-smooth muscle (all cell types)
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What is the function of myosin VI.
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Move things around inside cell (similar to myosin I) except moves towards the (-) end
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What is the function of myosin V?
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Move things around inside cell (similar to myosin I)
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What is (myosin I) MHC I and its function?
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MHC I has single domain of Motor and Tail which the tail is short and unable to provide the same type of movement as Myosin II. MHC I moves towards the + end of microfilaments carrying cargo. Important in microvilli where is links microfilament to cell membrane
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What are the steps to cell motility?
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1. extension = lamellipodia and filopodia move arm towards direction of movement (constant polymerization and depolymerization) 2. Adhesion = Lamellipodia and filopidia attach 3.Retraction=cell moves forward and leave part of cell left behind. So actin polymerization is involved in moving lamellipodia but the mysoin interaction is what helps move the entire cell. To get a stable attachment must engage in cell surface receptors like Integrin receptors
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What are intermediate filaments?
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Heterous group of proteins that provide mechanical and structural support like linking organelles. They are not dynamic (no ATP). Specific expression in certain cell types so can recognize the origin of tumor cell
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What is the struture of intermediate filaments?
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have central α helical rod domain of polypeptide head of tail that align in anti-parallel protein dimers to produce tetramers which align end to end to form protofilaments. Intermediate filaments are made of 8 protofilaments (rope like)
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What are desmosomes?
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Attachment from cell to cell that involves intermediate filaments
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What are hemidesmosomes?
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Attachment from Cell to extracellular matrix that is stabilized by intermediate filaments (not dynamic only structural)
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Give an example of disorders of hemidsmosomes?
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Epidermolysis Bullosa Simplex: The hemidesmosomes are supposed to connect epidermis to dermis, but it doesn't so blisters form. Similar to how babies skin falls off with the genetic disorder
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What are desminopathies?
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Cardiac and skeletal myopathes caused by mutation in desmin gene (desimin is an intermediate filament that maintains structural integrity of contractile apparatus)
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What is the structure of microtubules and its assembly?
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αtubulin (has ATP attached) and β tubulin(has GTP that gets hydrolyzed during microtubule assembly) form heterodimer that join to form a protofilament. 13 protofilaments make a microtubule that is thick and hollow. The + end builds and the - end breaks down the heterodimer so has treadmilling effect. The + end has the GTP and is hydrolyzed further down except when there is low levels of GTP so then the + end can break down (dynamic instability)
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What are MAPs?
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microtubule associated proteins= proteins that regulate behavior of microtubules that aid in assembly, stabilization, cross-linking, tracking, destablization, and severing
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What are specialized structures of microtubules structures?
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Cilia and flagella have axoneme core structure of 9+2 array and basal bodies derived from centrioles. Dynein connect tubules and move towards + end (motor head) that causes bending of anchoring of nexin
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How do microtubules transport macromolecules, organelles, and vesicles?
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1. Kinesins: "kick out" carry out cargo to + end and 2.Dyneins: "drag in" carry in cargo to - end. These proteins consist of head domain that has ATPas and "walks along microtubules and a tail domain that carries cargo
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What is the role of microtubules in Alzheimer's disease?
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the microtubule Tau is hyper-phosphorylated and causes intraneuranol lesions
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How does chemotherapy effect microtubules?
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Chemo targest microtubules which is essential to cell division so tumor cells can't survive
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