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33 Cards in this Set
- Front
- Back
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What is the cytoskeleton composed of?
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Actin - smallest, made of actin
Microtubules - largest, made of tubulin Intermediate Filaments - middle, made of fibrous proteins like vimentin, keratin and lamini |
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What are the four functions of the cytoskeleton?
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1. cell structure
2. toughness 3. movement of materials within cells 4. actual movements of cells |
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What are some general facts about the cytoskeleton?
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1. found only in eukaryotes
2. highly dynamic structures 3. allows cells to respond to environment 4. cell movement, muscle contraction, shape change during embryo development 5. intracellular movements like organelle transport and chromosome segregation |
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What are two specific things about the plasma membrane?
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1. proteinacceous skeleton referred to as the cortex
2. spectrin dimers - associate head to head to form tetramers |
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What is the difference in actin between nucleated cells and erythrocytes?
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Actin is MORE abundant IN nucleated cells
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What is the main function of the intermediate filaments?
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To resist stress and strain!
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What happens to patients suffering from Epidermolysis bulosa simplex?
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The IM-keratin is mutated.
-easy blistering b/c of rupturing of the basal layer -as baby is born most of the skin is removed! eeewwww |
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What is the Nuclear Lamina composed of and what is it associated with?
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The nuclear lamina is made of IM-Lamin
It is associated with both the chromatin and the inner nuclear membrane |
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Where are IM filaments located?
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-IM filaments are found in the nuclear lamina (think nuclear pores)
- are activated during mitosis for the reversible disassembly/assembly via phosphorylation and dephosphorylation -in concentric layers outside the nuclear membrane -attached to the plasma membrane at desmosomes or hemidesmosomes |
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What are the nm diameter sizes of Actin, IM-filaments, and Microtubules?
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Actin: 5-9 nm
IM-filaments: 8-nm Microtubules: 25nm (the smallest viruses are 10nm) |
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Explain the 5 step mechanism of IM-filament structure.
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1. start with an IM-monomer
2. dimerize 3. a) central rods align in parallel and wind into a coil 3. b) two dimers line up anti-parallel to form a tetramer 4. dimers stagger within tetramer; tetramer units can interact 5. tetramers packaged into rope-like configurations |
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How are the keratin filament networks connected to one another?
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They are connected indirectly through desmosomes (Cell to Cell) and also the basal lamina through hemi-desmosomes (Cell to Matrix).
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What are microtubules made of and what is the function of MT?
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MT are comrpised of Tubulin (2 subunits, alpha and beta)
MTs are responsible for the movement/transportation of membrane bounded organelles. |
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What is the basic composition of the MT tube?
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MT tubes are hollow rods made of 13 side-by-side rods.
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Explain the polarity of the MT.
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MT (+) ends grow rapidly during assembly. This is a type of polymerization and is graphed sigmoidally.
This process is called DYNAMIC INSTABILITY |
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Several drugs interact with MT "Dynamic Instability." How do the following drugs function?
-Colchicine -Colecemid |
Colchicine - treats Gout, binds tightly to Tubulin & prevents polymerization. IRREVERSIBLE. Inflammatory cells can't migrate into joints (affects motility) ALSO prevents phagocytosis of accumulated urate cyrstals [...] no release of inflammatory mediators.
Colecemid - closely related but is REVERSIBLE |
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Several drugs interact with MT "Dynamic Instability." How do the following drugs function?
-Vinblastine -Vincristine |
Both treat cancer by interfering with MT polymerization. Tubulin dimers aggregate.
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Several drugs interact with MT "Dynamic Instability." How do the following drugs function?
-Taxol |
Treats cancer by interfering with MT structure & thereby function. Taxol binds DIRECTLY to MT and prevents de-poly. MTs are stabilized.
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What is a nucleator?
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Nucleator, aka: centrosome, basal body, spindle pole. This is where the (-) ends of the MTs bind
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How do cells move via cilium or flagellum?
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Cell motility is caused by Microtubules. MT structures called AXONEME bend and produce the movement of cilium and/or flagellum.
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What is ciliary dynein?
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Ciliary Dynein is a motor protein associated with Microtubules. It generates a sliding force to move the complex. Hydrolyzes an ATP.
Cilia are found in the esophagus amongst other places |
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How do Microtubules play a role in cell division?
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The centrosome is the major MT organizing center. During cell division, the centrosome splits in two, each 1/2 containing a centriole.
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In what cellular process do Kinesin and Dynein play a role?
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During organelle transportation via the ER, Golgi, and vesicles, Kinesin and Dynein drive the rate and direction of organelle movement along a microtubule.
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Which end to Kinesins move and which ends to Dyneins move?
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Kinesins - vesicles more outwards to the (+) end. Think "KY" towards the CYtoplasm."
Dyneins - vesicles move towards the (-) end. Think "NEgative ends towards the Nucleus." |
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What is the role of a capping structure?
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Capping structures (involves GTP) are important in controlling DYNAMIC INSTABILITY for MICROTUBULES. Capping ends are placed on the (+) ends.
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Actin (which can be thought of as two helical stacks), can be found in which two forms?
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1. G Actin - soluble monomer
2. F Actin - filaments |
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Which two cytoskeletal components have nucleotide-binding sites?
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Actin by Actin-ATP.
Microtubulues by tubulin. |
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In an Actin filament there are plus and minus ends, which end grows rapidly?
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In actin filaments, the (+) end grows rapidly, whereas slow growth occurs at the (-) end.
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What are the three basic functions of actin?
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1. Dynamic activities in the leading edge of crawling cells.
2. A structural role in the cortex of some epithelial cells. 3. The functional role in skeletal muscle cells. |
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What is 'crawling' when it comes to the cytoskeleton?
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Referring to the actin-associated protein FIMBRIN, crawling cells throw out microspikes and filopodia. They can be found as single protrusions, sheets, or invaginations.
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What do the following terms have to do with cytoskeletons?
-Cortex -Gel -Filamin -Contractile bundles |
Cortex - proteinaceous skeleton of the plasma membrane
Gel - actin organization style with right-angles Filamin - actin-associated protein supporting crossover points Contractile bundles - composed of actin filaments behind Filamin |
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What do the following terms have to do with cytoskeletons?
-Alpha-Actinin -Myosin-I -Gelsolin -Thymosin |
Alpha-Actinin - cross-linking protein widely spacing the contractile bundles
Myosin-I - motor protein Gelsolin & Thymosin - filament severing protein. Binds to actin monomers and regulates ability to enter filaments |
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What is the main function of microvilli and what is it composed of?
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Microvilli increase the amount of absorptive surface area . It is made of parallel actin filaments held together by villin and fimbrin.
(intestines - absorption, secretion, cellular adhesion) |
