Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
10 Cards in this Set
- Front
- Back
|
Functions of Cytoskeleton (4)
|
Maintaining and directing cell structure
Intracellular transport (organelle and vesicle movement) Spatial organization of cell Contractility and Mobility (actin/myosin contraction, movement of cilia and flagella, chromosome movement, cell migration-amoeboid movement) |
|
|
Cytoskeleton is formed from:
|
Microtubules
Intermediate filaments Microfilaments |
|
|
Techniques for VISUALIZING the cytoskeleton (3):
|
1. fluorescence microscopy
-immunofluorescence: use of antibodies against cytoskeletal proteins (immunocytochemistry) -use of fluorescently tagged drugs that bind to cytoskeletal proteins (e/g/ phalloidin, binds to actin filaments) 2. Electon microscopy (especially of freeze-etched surfaces) 3. Video-enhanced light microscopy-can detect presence of tubules and filament bundles, and follow movement of vesicles in living cells |
|
|
A technique for studying the cytoskeleton (using genetic engineering) is knockout mutants. Explain what that is and give an example.
|
-developing genetically engineered organisms of cell lines that lack a cytoskeletal or motor protein (knockout mutants)
-ex. mouse embryos that lack a motor protein called cytoplasmic cynein fail to develop beyond 8 days due to dispersion and fragmentation of the Golgi complex, suggesting a role for dynein in maintaining the structural integrity of the Golgi complex |
|
|
Alternative techniques to making "knockout" mutants (2):
|
1. Cell lines or organisms engineered to over-express a "dominant negative" form of a cytoskeletal protein
-these cells may show defects in specific functions of that protein similar to that of knockout mutants -dominant negative mutant proteins are non-functional proteins that compete with the native protein and inhibit its function 2. Cell that are engineered to express "small interfering" RNA sequences (siRNA's) targeted to be complementary to the mRNA's of specific cytoskeletal proteins may also show defects in functions associated with those proteins -siRNA binds to the specific mRNA that has the complementary sequence, promotes its destruction and silences the translation of the protein that the mRNA specifically codes for |
|
|
Microtubules form what structures? (3)
|
1. mitotic spindles of dividing cells
2. the core of cilia and flagella 3. a network of rigid tubules that radiate through the cytoplasm of all eukaryote cells |
|
|
Microtubules are formed from what?
|
Alpha and beta tubulin, globular proteins-approx 50kDa M.W.
Tubulins are a diverse family |
|
|
Microtubule structure
|
A rigid tube, whose wall is made from approx 13 protofilaments, composed of alternating alpha and beta tubulin rows
Microtubules are approx 25 nm in diameter and up to a micron or more in length The filament is polarized with a + and - end (+ end usually grows faster during microtubule assembly), which has nothing to do with electrical charge The + end has a row of beta, and hte - end has alpha tubulins |
|
|
Proteins that bind to microtubules: (2)
|
1. Motor proteins-kinesins and dyneins
2. MAPS (microtubule associated proteins)-proteins that cross-link MT's or regulate their assembly -binding of MAPS to microtubules is regulated by their phosphorylation (e.g. the Tau protein, which regulates microtubule assembly in neurons)(over-phosphorylation of tau may be involved in creating the tangled neuronal structures observed in Alzheimer's Disease patients) |
|
|
Two drugs that affect microtubules:
|
Nocodazole-prevents microtubule assembly
Taxol-prevents microtubule disassembly -both drugs are anti-mitotic (prevent cell division) because chromosomes cannot assemble and separate -Taxol is an accepted chemotherapy agent for cancer treatment since it will prevent the rapid division of tumor cells (but it also prevents mitosis in all other cells, e.g. hair follicies, leading to hair loss) |
