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43 Cards in this Set
- Front
- Back
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What cytoskeleton element is the strongest and why? |
Intermediate filaments because they are dynamic and similar to a rope |
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Structure of IF |
Strong, ropelike fibrous proteins that are supercoiled into thick cables |
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Diameter of IF |
8-12 nm |
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Protein subunits of IF |
Keratin family types |
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Main function of IF |
Cell shape, nuclear envelope support, and mechanical stress |
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Structure of microtubules |
Hollow tubes that consist of 13 columns of tubulin |
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Diameter of microtubules |
25 nm with 15 nm lumen |
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Protein subunits of microtubules |
Alpha and beta tubulin |
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Main function of microtubules |
Cell shape, cell motility ( flagella), chromosome movements, organelle support |
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Structure of MF |
Two intertwined strands of actin |
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Diameter of MF |
7 nm |
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Main function of MF |
Cell shape lamelopodia cytoplasmic streaming cell motility and cell division (Cleavage furrow) |
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Desmosomes |
intermediate filaments are indirectly connected to those in neighbouring cells via desmosomes IF's are anchored to the plasma membrane by protein plaques |
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Assembly and Disassembly of IF's |
Most IF's are full polymerized providing a fairly stable structure to the cell Disassembly prior to cell division and reassembly after cell division |
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Functional Characteristics of If's |
Great tensile strength |
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Cytoplasmic IF |
Keratins (epithelia) Vimentin ( CT, muscle cells, neuroglia cells) Neurofilaments Desmin ( muscle cells) |
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Nuclear IF's |
Nuclear lamins - animal cells |
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Why are IF's important in cancer screens? |
Diagnostic markers - can tell you where the cancer has originated- many tumor cells change and make weird proteins but the basis can still befound |
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Where are microtubules found? |
Neutron cells Mitotic spindle Cilia and flagella |
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Each protofilaments of microtubules have polarity- what does this mean? |
Beta- tubulin = plus end - polymerization occurs Alpha tubulin = minus end |
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Functional Characteristic of microtubules |
Generate movement - form spindles used to move chromosomes apart - Help move items down axons - Movement of cilia and flagella |
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What is the MTOC? |
microtubule organizing centre The plus end of the microtubules has fast growth and the microtubules grow through the MTOC during metaphase (centrosome and centrioles) |
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GTP and microtubules |
GTP can promote growth GTP hydrolysis (by tubulin) - depolymerization and shrinkage |
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Microtubules in centrioles |
Pericentriolar material (PCM) initiates formation of microtubules Microtubule minus end is in centriol |
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Microtubules in basal bodies and other MTOCS |
Cilia and flagella - identical in structure to centrioles |
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How are microtubules arranged in centrioles and centrosomes |
nine sets of microtubules arranged in triplets |
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How are microtubules arranged in flagella |
nine sets of microtubules arranged in doublets plus two in the centre |
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What is basal body |
the base of each cilium or flagellum |
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How are cilia and flagella similar? |
They have the same internal structure but the differ in length Both cause motility |
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Motor proteins |
Kinesins and dyneins are MT motor proteins that move in opposite direction along a MT - Axon transport |
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Dynein |
ATP dependant walking Move toward minus end of MT |
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Kinesins |
Two heavy chains and several light chains Globular heads are enzymes with ATPase activity move toward plus end of MT |
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Anti mitotic alkaloids |
Colchicine Taxol |
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Colchicine |
Binds to free tubulin Arrests chromosomes in metaphase and prepare karyotypes |
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Taxol |
Binds to MT's and prevents them from losing subunits- new subunits can be added Used to arrest proliferation in tumor cells |
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monomer subunits of Actin filaments |
G-actin monomers associate to from F-actin filaments - 2 F-actin filaments binds to form actin filament |
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Actin filament polarity |
Plus end- assembles/ disassembles faster minus End - slower |
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Functional Characteristic of actin filaments |
Acting with myosin can form contractile structure |
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lamellipodium |
dynamic sheetlike extension on the surface of the animal cell - fibroblasts |
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Filopodium |
Long thin actin containing extension on the surface of the cell - fingerlike |
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Actin filament treadmilling |
Exchange of ADP from minus end to ATP for plus end and then hydrolysis of the ATP to ADP Net gain of subunits at plus end and same net loss of the subunits at the minus end |
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Function of actin filaments - cell crawling |
Cell cortex Actin filaments are linked by actin binding proteins into meshwork that supports outer surface of cell Cell crawling depends on acting |
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Actin binding proteins |
Spectrin and Akyrin |
