Week 8
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What make up the cytoskeleton?
Actin filaments, Intermediate filaments, Microtubules
What is the important function of the cytoskeleton?
Muscular movement to the transport of molecules thorough out the cell. Normal embryonic development.
Abnormalities in the cytoskeleton result in what?
Diseases affecting every tissue in the body. Many drugs work by targeting the cytoskeleton. And can be cancer treatment by interupting cell division
What is the structure of microfilaments?
Two intertwined strands of actin, each polymer of actin subunits 7nm in diameter
Function of microfilaments?
Maintenance/change of cell shape, Muscle contraction, Cytoplasmic streaming, Cell motility, Cell division, Exo/endocytosis, Cell junctions
What are microfilaments made of?
G and F actin (G assembles into long, helical F-actin polymers) ATP holds together the two lobes of the actin monomer
What are cellular extensions driven by?
Actin polymerization
Do microfilaments have microvilli?
Yes. Allows movement of cells, Increased absorption, Also allows sound absorption
What are actin motor proteins?
Myosins (I, II, V (different functions according to shape) hey use energy derived from ATP hydrolysis to “walk” along actin filaments. Enables roles in contraction or transportation
What is Phalloidin?
Toxins that bind to F-actin preventing disassembly. Can be used as a florescent tag to stain actin. Treatment can be eating red meat.
true or false, actin is a globular protein?
true
What is the structure of microtubules?
Hollow tubes, wall consists of 13 columns of tubulin molecules 25nm diameter, with 15nm lumen
What are the functions of microtubules?
Maintenance of cell shape, Cell motility, Chromosome movements in cell division, Organelle movements
What are the protein subunits of microtubules? (tubulin polymers)
Tubulin, a dimer consisting of a-tubulin and b-tubulin
What is the importance of microtubule-binding drugs?
Used to treat a variety of diseases, including cancer. EG the cancer drug taxol used for ovarian cancer, breast cancer and lung cancer which prevents microtubule disassembly and therefore cell division in cancer cells.
Size of cilia vs flagella?
Cilia - 2-20um Flagella - 10-200um However, both have the same stucture
What are the two main types of microtubules?
cytoplasmic - more dynamic and loosely organized found in the cytoplasm. axonemal - highly organized and stable found in cilia flagella and basal bodies
how are microtubules formed?
By polymerization of tubulin dimers
What is the role of cytoplasmic microtubules?
maintenance of cell shape, cell movement, transport of vesicles within the cell and the separation of chromosomes during cell division.
What is the structure of intermediate filaments?
Fibrous proteins supercoiled into thicker cables. 8-12nm in diameter
Intermediate filament protein subunits?
One of several proteins (eg keratins), depending on cell type
Functions of intermediate filaments?
Maintenance of cell shape, Anchorage of nucleus and certain other organelles, Formation of nuclear lamina,
What can intermediate filament abnormalities lead to?
Amyotrophic lateral sclerosis (ALS)
What is the main function of cell junctions?
Form a barrier, provide structure