BIOC290_5 Cytoskeleton Final 2Mv PDF

The Cytoskeleton  The Cytoskeleton- Introduction For cells to function properly, they must.. organize themselves in space interact mechanically with each other and with their environment correctly shaped physically robust properly structured internally change their shape and move...

The Cytoskeleton  The Cytoskeleton- Introduction For cells to function properly, they must.. organize themselves in space interact mechanically with each other and with their environment correctly shaped physically robust properly structured internally change their shape and move from place to place move from place to place able to rearrange their internal compartments as they grow, divide, and adapt to changing circumstances.  What is Cytoskeleton These spatial and mechanical functions depend on a remarkable system of filaments called the cytoskeleton The cytoskeleton: A complex and dynamic network of protein fibers that extend throughout the cytoplasm of a cell and form the structural framework of the cell, providing the: – skeleton & muscle of the cell – support, motility, and regulation. The cytoskeleton what holds the organelles in place, or moves them and helps in cell movement. Important features (functions)of the cytoskeleton Gives the cell its shape. Provides protection by mechanical resistance to deformation. Actively contract, deforming the cell and the cell's environment and allowing cells to migrate. Involved in many cell signaling pathways. Involved in the uptake of extracellular material (endocytosis). Separates the chromosomes during cellular division, and the cytokinesis stage of cell division. Scaffolding to organize the contents of the cell in space and in intracellular transport (for example, the movement of vesicles and organelles within the cell). Can be a template for the construction of a cell wall. It can form specialized structures, such as flagella, cilia, lamellipodia and protostomes.  Types of Cytoskeleton The three major cytoskeletal filaments are responsible for different aspects of the cell’s spatial organization and mechanical properties. See this video on cytoskeleton types: https://app.jove.com/embed/player?id=13924&access=393f411555&t=1&s=1&fpv=1 Actin filaments (microfilament) determine the shape of the cell’s surface and are necessary for whole-cell locomotion; they also drive the pinching of one cell into two during cell division Microtubules determine the positions of membrane-enclosed organelles, direct intracellular transport (act as tracks for kinesin and dynein. These transport cargo and vesicles from one place to another in the cell), and form the mitotic spindle that segregates chromosomes during cell division. Microtubules bind different MAPs (microtubule-associated proteins), microfilaments and intermediate filaments to maintain cell shape. For details, see this video on alpha & beta tubulins (in relation to MTOC-microtubule organizing center): https://app.jove.com/embed/player?id=11906&access=f15695aa62&t=1&s=1&fpv=1 Intermediate filaments provide mechanical strength Types of Cytoskeleton The cytoskeleton’s varied functions depend on the behavior of three families of protein filaments: actin filaments, microtubules, and intermediate filaments Each type of filament has distinct mechanical properties, dynamics, and biological roles However, all share certain fundamental features, so all three cytoskeletal filament systems normally function collectively to give a cell: its strength, its shape, and its ability to move. Cytoskeleton All of these cytoskeletal filaments interact with hundreds of accessory proteins that regulate and link the filaments to other cell components, as well as to each other The accessory proteins are essential for the controlled assembly of the cytoskeletal filaments in particular locations. The accessory proteins include the motor proteins, remarkable molecular machines that convert the energy of ATP hydrolysis into mechanical force that can either move organelles along the filaments or move the filaments themselves  Microfilaments Actin filaments / microfilaments Helical polymers of the protein actin-polymerize to form long and thin fibers (e.g. G-actin polymerizing to form F- actin filaments) Diameter – 7-8 nm Represent the active or motile part of the cytoskeleton