BIS104 Note10

BIS104 Note10 - Lecture 10 Bio Sci 104 Cytoskeleton Winter...

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Lecture 10 1 Bio Sci 104 Winter 2010 Cytoskeleton I. Overview Without a cytoskeleton, everything would be spherical (energy minimization) and cells would not be able to connect with one another to form tissues. Furthermore, the subcellular organelles would float around in the interior randomly, vesicular transport would be impaired, the complex process of replication, that involves segregation of chromosomes and the physical division of the daughter cells, would be impossible, and your skin would rip apart from the simple stress of rubbing against your clothing. A. The cytoskeleton is responsible for the overall shape, structure, and movement of the cell The cytoskeleton controls the shape of a wide variety of different cell types. For example, the axon of a single neuron can be over a meter long, the cytoskeleton makes this possible. It is also responsible for providing mechanical forces such as those in muscle contraction. The cytoskeleton also makes up your skin, hair and nails. And it allows cells such as white blood cells to crawl. One last example, the cytoskeleton creates the flagellum needed for sperm movement, and cilia in your lungs. B. The cytoskeleton is responsible for internal organization of the cell This includes mechanical support of membranes, formation of microvili in your gut that increases the surface area of a cell, or the hair cells of your ear. Without the cytoskeleton, the secretory pathway would fail. The cytoskeleton moves vesicles from ER to Golgi to plasma membrane, and positions the organelles of a cell. The cytoskeleton is also essential for chromosome segregation in mitosis and cytokenesis to complete cell division. - Cytoskeleton forms a highly dynamic structure that reorganizes continually as cell changes shape, divides, and responds to environment. C. Three classes of filaments Microtubules (MT ) -intracellular transport, mitosis Actin Filaments (AF) -determine a cell’s shape, locomotion, cytokenesis Intermediate Filaments (IF) -Provide mechanical strength and resistance to shear Many other proteins bind to these cytoskeletal filaments to regulate their organization, to link cytoskeleton to other elements of the cell, or to act as motor proteins. These accessory proteins play important roles in controlling assembly and three-dimensional structure of the different cytoskeletal filaments. D. Intrinsic biochemical properties of filaments 1. The cytoskeleton is highly dynamic and adaptable. -It is more like an ant trail than a permanent paved highway, constantly adapting to
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Lecture 10 2 its environment. -Filaments are made from a pool of free subunits, there is an equilibrium between monomers and filaments. This equilibrium is highly regulated by accessory proteins in the cell. 2. Rate constants
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BIS104 Note10 - Lecture 10 Bio Sci 104 Cytoskeleton Winter...

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