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Actin.Myosin - http/www.wiley.com/college/pratt/04713...

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http://www.wiley.com/college/pratt/04713 93878/student/animations/actin_myosin /actin_myosin.swf The Actin Cytoskeleton Actin is the component of the cytoskeletal system that allows movement of cells and cellular processes. It works in conjunction or in tandem with other components of the system. Like the other components, it can undergo constant rearrangement to produce movement. Actin filaments are also called microfilaments, or "thin filaments" to distinguish them from intermediate filaments. Read pp 42-44 in Gartner and Hiatt Test yourself: How much do you know about the Actin cytoskeleton? 1. Describe the actin monomer . 2. How is the polymer formed ? What ingredients do you need to make an actin filament? 3. Actin filaments, like microtubules, have polarity. How is polarity defined in actin. What macromolecule can you use to detect polarity ? 4. Which end of actin filaments polymerizes more rapidly? 5. Describe the process of nucleation and elongation of actin filaments. 6. What are effects of cytochalasin D on actin filaments? 7. How does profilin promote actin assembly ? 8. What are roles for severing proteins (gelsolin and cofilin) in cell motility? 9. How does the actin cytoskeleton regulate projection of cellular processes ? 10. What are focal adhesions and what is their significance? How do focal adhesions differ from hemidesmosomes? 11. How is actin organized in microvilli ? 12. Myosin is similar to kinesin in two ways. Name these similarities. 13. How does myosin II interact with actin in epithelial or dividing cells? 14. Describe the steps involved in cell movement including: extension of the cell membrane, formation of focal adhesions, movement of the cell body and deadhesion. What are stress fibers? Compare the "chemistry of the front and rear of a moving cell". 15. How do sol and gel states of the cytoplasm relate to cell movement? b) How might calcium be involved? c) Where are myosin I and myosin II involved? Describe the actin monomer. Actin is a globular protein with an ATP binding site in the center of the molecule. Termed "G-actin" the monomer will dimerize or form a trimer. This serves as a site for nucleation and further growth of the actin protofilament. Below each structure represents G-actin.
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ATP is hydrolyzed immediately after the molecule is incorporated into an actin filament. The ADP is trapped in the actin filament until it depolymerizes. Then an exchange can occur. How is the polymer formed? What ingredients do you
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Actin.Myosin - http/www.wiley.com/college/pratt/04713...

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