BCOR 103 1st Edition Lecture 8 Outline of Last Lecture I The Chemiosmotic Theory of ATP Production II ATP Synthase III Professor answered questions for exam rest of class chloroplasts will not be included on the exam Outline of Current Lecture I The Cytoskeleton II Cytoskeletal Structures III Filament Assembly IV Dynamic Instability Current Lecture The cytoskeleton is the architectural material of the cell The key activities that it is associated with are cell shape positioning organelles macromolecular metabolism a track for the transport of materials within the cell cell movement and transduction between cells Cytoskeletal Structures Filament System Microtubules Intermediate Filaments Microfilaments Thick Filaments Major Protein Subunit Structure Diameter Major Function s Hollow Tube 22nm Cell Polarity Cell Division Intracellular Transport Variable Fibrous Protein Rope like Fiber 10nm Basic Support Cell Shape Resist Stress Actin Globular Protein Chain 6nm Cell Elasticity Cell Motility Myosin Muscle like Rough Bipolar Fiber 15nm Contractility Tubulins These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Intermediate Filament Proteins assemble in a building block like sequence Starting with one helical region then a coiled dimer of the two then a combined staggered dimer the association of eight tetramers which come together to make up filaments This building block process produces a stress resistant filament There are N and C terminal domains that project to the surface to provide binding sites for other components Without filaments a layer of cells would not stretch and remain intact they would rupture Dynamic Instability refers to the growth and collapse of microtubules A growing microtubule lengthens when GTP binds to tubulin molecules The microtubule can collapse when GTP hydrolysis occurs and the microtubule peels itself away Additionally some microtubules become stable when they meet a capping protein at the cell membrane Others do not get capped and so they grow and shrink over and over
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