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36 Cards in this Set
- Front
- Back
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kinesin
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-move from - to +.....out of cell
globular heads have atp binding sites heads bind to microtubules and initiate atpase activety |
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1)cargo
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vesicles, protein complexes and organelles, which are bound to specific members
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what binds kinesin to cargo?
what binds dyneins to cargo? |
1) kinectin
2)dynactin |
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most cells, not just axons, are supportd by what?
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arrays of microtubules
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where is the + and - end of microtubules?
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+ end points away from the middle of the cell
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which direction to dynein and kinesin travel?
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dynein moves things toward the middle of the cell +to-
kinesin moves things away from the middle of the cell: - to + |
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dynein
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microtubules based motor protein
two atp bingding heads...just like kinesin move from + to - |
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name one big function dyneins can be involved in
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positioning the spindles for chromosome movement during cell division
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draw a picture of kinesins and dyneins involved in transport with golgi complex, ER and the otside of cell
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aa
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how can microtubule assembly be achieved in vitro
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from a homogenate cell mixture or from purified alpha, beta tubulins
-add mg2+, gtp and egta |
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what does egta do in vitro for microtubule assembly
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binds Ca2+ which inhibits assembly
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how can assembly/dissassembly of microtubules be cycled through
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raisings and lowering the temperature
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in vitro, how can microtubule assembly be sped up>
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by adding existing microtubule fragments
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what does assembly of microtubules in vitro and vivo begin with?
requires? |
creation of dimers between alpha and beta tubulin
GTP molecule bound to beta-tubulin |
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what happens after gtp binds to beta-tubulin
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dimers associate into microtubule fragments, and then the microtubule elongates
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where would you expect to find gdp and gtp on a microtubule?
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gdp - end
gtp + end (cap will stabalize the + end) |
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what does gtp bind to in microtubules?
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beta tubulin
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what happens to gdp on the tubulins when they disasseble?
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replaced by a new gtp after dissassembly of the microtubule back into tubulins
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gtp dimers
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gtp binded to beta tubulin when it forms the chain
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how can the growth or shrinkage of microtubules be regulated
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mainly by altering the balance of addition and removal of tubulin dimers
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katanin
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can cut microtubules into pieces, exposing the (-) end for depolymerization
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MTOC
ex. |
microtubule organizing centers
play a role in nucleation ex. centrosomes basal bodies others scattered in plant cells which lack centrosomes |
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2 microtubule phases
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nucleation and elongation
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nucleation
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small portion of tubule formed at the begining
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are centrosomes found in all animal and plant cells?
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no they are only found in every animal cell
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when do centrosomes divide
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before cell division begins
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PCM
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peri-centriolar material
surounds the centrosome |
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draw and describe centrosome structure
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Centrosome
One found in each animal cell. Divides before cell division begins. A complex structure with two barrel-shaped centrioles – 0.2 micrometers in diameter and twice as long - surrounded by electron-dense peri-centriolar material (PCM) Centrioles contain nine fibrils in a pinwheel pattern, each composed of three microtubules A,B,C B,C are fragments that “piggyback” onto A The pair of centrioles in a centrosome are at right angles to each other. Large numbers of microtubules converge onto the centrioles. |
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how can microtubule assembly be studied in living cells
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depolorizing them into tubulins with cold or drugs
re-polimerization occurs when the drugs are washed out or heating occurs bix cells at various times and stain them with fluorescent anti tubulin antibodies |
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what will be seen when studying microtubule assembly in cells
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within 15-30 minutes of removing the drug or heating, microtubule re-assembly occurs
the + end will radiate outwards and the - end will be found in the PCM |
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do all microtubules originate at the cetrosome?
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no
microtubules in the axons of neurons originate in cytoplasm throughout the length of the axon |
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microtubules in axons do what with respect to the centrosome?
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possibly polymerize there
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oocytes
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egg precursors
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mouse oocytes importance
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do not have centrosomes yet still form mitotic spindles
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basal bodies
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non-centrosome MTOCS
found at the base of cilium or flagellum identical in structure to the centrosome |
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describe pcm
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pericentriolar material
has gamma tubulin will only bind to alpha tubulin |
