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18 Cards in this Set
- Front
- Back
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What are the functions of the cytoskeleton?
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1. Structure and support.
2. Spatial organization 3. Intracellular transport 4. Cellular contractability: force generation (motility) |
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What is the function of IF?
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To provide mechanical strength to cells that experience physical stress: neurons, muscles, and epithelial cells lining body cavities.
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What is the structure of IF?
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Most IF's share a similar structure because their polypeptides have similar structural organization. The filaments are: central, rod shaped, alpha-helical domain of similar length: 7 heptad repeat.
Can be N and C terminal: varies. 2 monomers: coiled-coil motif: polar dimer: 7 heptad repeats interact and form 2 dimers: tetramer. The functional subunit is now nonpolar. Form filaments: linear structure of many tetramers. 2 filaments: profibril 4 profibrils: 1 IF |
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What are some characteristics of IF?
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Least dynamic of the 3 elements.
Can breakdown and reform, but usually pretty stable. Subunit incorporation is along the length of the IF, not at ends. IF are key components of desmosomes and hemidesmosomes. |
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What are the functions of MT?
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1. Structural support. They are stiff and can resist compression of bending of fibers. Are a reflection of cell shape and can produce pathways.
2. Import in motility. Use motor proteins. 3. Cilia, flagella 4. Mitotic spindle/chromosome movement. |
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What are some characteristics of MT?
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Polar
B subunit: (+) and fast-growing Alpha subunit: (-) and slow-growing. Composed of a heterodimer of alpha and Beta tubulin. Cylindrical in structure doublets, triplets, and singlets. Cilia/flagella: 9 doublets and 2 singlets centrioles/basal bodies: 9 circular |
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What is the structure of a doublet MT?
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13 protofilaments and 1 more. 3 are shared
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What is the structure of a triplet?
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13 + 10 + 10
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What are basal bodies?
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Occur at the base of cilia and flagella. Have same structure as a centrosome. Type of MTOC
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What are MTOC?
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9 triplets arranged in circle.
Control the # of MT formed, polarity, regulate the # of protofilaments, regulate timing and location of MT assembly Nucleate MT |
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Describe the centrosome.
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Role: nucleates MT.
2 centrioles surrounded by PCM. The centrioles are duplicated in S with DNA. The daughters are produced perpendicularily to mother. |
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Microtubule Assembly.
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Not included in flashcard. Look in class notes/ book.
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What is the function of MF?
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1. Contractile processes: actin/myosin.
2. Motility: intracellular transport. |
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What are the motility processes that MF are involved in?
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1. Amoeboid movement
2. Microscopic processes of neurons 3. WBC/macrophages: "crawling" 4. Would healing: epithelial cells 5. Neuronal crest cell migration during embryonic development. |
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F-actin v. G-actin
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Not included. Look in class notes/book/research it.
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How are actin monomers incorporated into MF?
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1. Must be bound to ATP to be incorporated into MF.
2. Once incorp., ATp is hydorlyzed and destabilizes. Actin/ATP cap is present and MF continues to elongate. The barbed (+) end incorporated monomers faster than (-) end (in vitro) * (-) end preferred site for depolymerization. |
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What occurs at different concentrations of free actin monomers?
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High: subunits added to both ends, with higher affinity for (+) ends.
Less: (+) end still added, removed from (-) end. Even less: Treadmilling. |
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What is treadmilling in MF?
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The 2 rxns are balanced so length of MF and mount of free monomers of actin remain constant: steady state.
Subunits are added to the (+) end and removed from (-) end continuously so the relative position of the individual subunits is continually moving. |
