Chp 13 Flashcards
What is the cytoskeleton, and what are its major components?
The cytoskeleton is a network of protein filaments in the cytoplasm that provides structural support, shape, and organization to the cell. Its major components are microtubules, microfilaments (actin filaments), and intermediate filaments.
What are the primary structural and functional differences between microtubules, microfilaments, and intermediate filaments?
Microtubules are hollow tubes made of tubulin, providing tracks for organelle movement and cell division. Microfilaments are thin, flexible strands of actin, important for cell movement and shape. Intermediate filaments are rope-like fibers made of various proteins, providing tensile strength and mechanical support.
What are the subunits of microtubules, and how do they assemble?
Microtubules are made of α- and β-tubulin dimers, which assemble end-to-end to form protofilaments; 13 protofilaments align side by side to form a hollow tube.
Distinguish between cytoplasmic and axonemal microtubules in terms of function and structure.
Cytoplasmic microtubules are dynamic and involved in cell shape, transport, and division. Axonemal microtubules are stable and highly organized, forming the core of cilia and flagella for movement.
What protein composes microfilaments?
Actin.
What are the major functions of microfilaments in cells?
Microfilaments are involved in cell motility, muscle contraction, cytokinesis, maintaining cell shape, and intracellular transport.
How do lamellipodia and filopodia differ in actin organization and cellular function?
Lamellipodia are broad, sheet-like projections with branched actin networks for cell crawling. Filopodia are slender, finger-like projections with parallel actin bundles for probing the environment.
What are intermediate filaments composed of, and how do they assemble?
Intermediate filaments are composed of various proteins (such as keratins, vimentin, neurofilaments, lamins) that assemble into staggered tetramers, which then form rope-like fibers.
What are the 6 classes of intermediate filaments? Provide examples of cell types that contain each class.
Class I: Acidic keratins (epithelial cells)
Class II: Basic/neutral keratins (epithelial cells)
Class III: Vimentin (mesenchymal cells), desmin (muscle), GFAP (glial cells)
Class IV: Neurofilaments (neurons)
Class V: Lamins (all nucleated cells)
Class VI: Nestin (neural stem cells)
Explain the significance of intermediate filament typing in identifying cell types.
Different cell types express specific intermediate filament proteins, so identifying these proteins helps determine cell origin and is useful in diagnostics, such as distinguishing cancer types.
