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24 Cards in this Set
- Front
- Back
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What kinds of enzymes are most abundant in peroxisomes?
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Catalase and Peroxisomes.
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Describe the structure of a microtubule.
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20-25 nm in diameter. Hollow, rigid, non-branching. Form in a/b TUBULIN dimers. Grow toward + end (beta end).
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Where are the microtubules located?
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They exist in equilibrium with the a/b dimers in the cytoplasm. Also in cilia, flagella, centrioles and cell elongation.
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How are microtubules assembled?
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Most grow from the MTOC. Heterodimers assemble in sheets, called protofilaments (requires GTP).
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What two proteins are important in microtubule assembly?
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Gamma tubulin serves as the nucleation site.
MAPS regulate assembly, anchor and stabilize. |
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Which direction do microtubules assemble in?
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From neg to pos ends (alpha to beta).
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What is the function of dynein?
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Dynein is a motor protein that moves along the microtubule from the neg end to the pos end (from periphery to MTOC). ex: axonemal dynein causes movement of cilia and flagella.
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What is the function of kinesin?
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Motor protein that carry organelles from center to periphery of cell.
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What supplies the energy for the ratcheting movement of microtubules>
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ATP hydrolysis
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What are the 2 kinds of actin filaments?
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Polymerize spontaneously to form:
g-actin (globular) f-actin (filamentous) both have ATPase activity |
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What proteins regulate the function of actin filaments?
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Acting binding proteins, regulate function and polymerization.
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What are the functions of microfilaments?
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locomotion of cells (lamellipodia)
anchoring and movement of membrane prots form the core of microvilli extension of cell processes (filapodia) help maintain shape of apical surface |
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What are the characteristics of intermediate filaments?
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Great tensile strength, form a network throughout the cell, lack polarity, enzymatic activity, and dynamic instability
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What is the structure of intermediate filament?
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Helical monomers twist together to form a coiled coil. This pair coils with another pair to form a tetramer. Tetramers link up to form filaments.
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What are keratins and where are they found?
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A class of intermediate filaments found in cells of epithelial origin. Attach to keratins in adjacent cells via desmosomes.
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What is vimentin and where is it found?
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Most abundant intermediate filament found in mesoderm-derived cells.
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What are neurofilaments?
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Intermediate filaments that extend from the soma to the axon of a neuron, provide structural support.
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What are lamins, and what do they do?
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Lamin A and Lamin B comprise the intermediate filament Lamin, which is associated with the nuclear envelope and provides structural support for the nucleus. Dephosphorylation causes them to assemble, phoph. causes disassemble.
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What happens if the plectin gene is mutated?
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Muscular dystrophy,epidermolysis bullosa, and neurodegeneration.
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What is the composition of a centriole?
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9 microtuble triplets form one centriole. A pair of centrioles lay orthogonally to each other. Lie in close proximity to nucleus.
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What is the relationship between the centrosome and the MTOC?
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They are the same thing. A region of the cell containing the centrioles and surrounding material. Presence depends on centrioles.
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What is the relationship between procentrioles and basal bodies?
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Centrioles replicate forming procentrioles that migrate to the cell surface and become the building blocks for basal bodies of microtubules of cilium or flagellum.
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What is the composition of the axoneme?
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The core structure of the cilium is two central microtubules surrounded by 9 doublets. The doublets are continuous with the A/B microtubules of the basal body.
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During what phase of the cell cycle does centriole replication take place?
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S phase! Mitotic spindle formation also occurs at this time.
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