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Cytoskelton, Cell Connections, ECM Cytoskeleton: structure (support), motility, movement - stabilizes animal cells by balancing opposing forces. - Anchorage of other organelles - Vesicles move along cytoskeleton as they move to plasma membrane or other organelles (endomembrane system). TYPES: 1. microtubules: hollow rods of tubulin protein subunits. - Can disassemble their tubulin and reassemble to assist in a cell changing shape Specific functions: 1. Maintenance of cell shape (compression bearing). 2. Cell motility (cilia and flagella) 3. Chomosomal movement 4. Organelle movement 1 Specific example #1 • cillia and flagella: - responsible for locomotion of motile cells (sperm, protists) Example #2: • framework for organelle attachment - guide for motion of organelles and proteins via motor proteins attached to membrane of organelles. 2 2. Microfilaments: Specific functions: 1. Maintenance of cell shape (tension-bearing) 2. Changes in cell shape 3. Muscle contractions (actin and myosin proteins… more later…) 4. Cell division 3 3. Intermediate Filaments: - More or less permanent structures – don’t disassemble and reassemble like microtubles and microfilaments Specific functions: 1. Maintenance of cell shape (tension-bearing) 2. Anchors nucleus (and other organelles) 3. Forms nuclear lamina Cell Connections Cells are organized into tissues and need to communicate so the tissue can function as a single unit. PLANT CELLS plasmodesmata: channels of cytoplasm through plant cell walls; connects the chemical environment of adjacent cells. Macromolecules can move along the cytoskeleton of a cell, move through plasmodesmata into adjacent cell. 4 5 ANIMAL CELLS desmosomes: fix animal cells together tight junctions: also hold animal cells together but form barrier to travel of extra-cellular fluids ex. Don’t want HCl leaking out of stomach to abdominal cavity! gap junctions (protein channels): cytoplasmic passages between animal cells; ions, sugars, and amino acids can move through… 6 Extracellular Matrix (ECM) = all the structures (stuff) between 2 cells - Structure: Proteins, Glycoproteins (w/specific carb shape & protein structure), fluid between neighboring cells 7 - Functions: o Communication between a cell and its environment o Regulatory: Effects development - Specificity of glycoproteins for each specialized cell type help to grow and develop specific tissues with specific jobs (developing embryo) Effects gene expression; therefore, the making of proteins. Animal Cells Collagen – most abundant glycoprotein in animal cells. Structural support for connected cells Fibronectin – glycoproteins that connect to proteins embedded in plasma membrane (through entire thickness) (integrins); o Integrins are further connected to the cytoskeleton attached to the inner side of the membrane. o This connection between Fibronectin (ECM) to integrins (through plasma membrane) to cytoskeleton helps cell communicate what is going on outside the cell to the inside and vise versa. 8 9