Cytoskeleton Chapter Pgs Objective: I can describe how the cytoskeleton is structured based on different protein fibers, and based on these, I can explain how a cell moves AND how objects move within the cell.
Cytoskeleton Description Internal network of protein fibers Think of as cell’s (cyto-) skeleton Function(s) Provide cell with structure, shape, support Anchor organelles; Provide Cell Motility Found in eukaryotes (only…?) NOT an organelle Protein fibers too small to be seen with light microscope – use fluorescent dyes
Made of 3 types of protein fibers Microtubules – most involved with movement Hollow tubes made of tubulin (thickest) Microfilaments – help change shape of cell + move Thinnest fibers made of actin Intermediate filaments – prevent excessive cell stretching (thick rope of intertwined proteins)
Microtubules - Details Microtubules grow from centrosome Centrosome = region near nucleus Microtubule-organizing center Contains a pair of centrioles Organelle?
Centrioles (more details) Part of cytoskeleton – help animal cells divide Made of microtubules (connects with rest) 2 sets of 9 triplets perpendicular to each other Centrioles similar structure with Basal Body Organelle, because evidence that evolved via endosymbiosis (resemble spirochete bacteria today)
Large Cellular Extensions Flagella (singular: Flagellum) Long, whip-like tail (movement only) Prokaryotes + Animal Euk. Cells Cilia (singular: cilium) Hair-like fuzz (movement + sweeping) Animal Eukaryotic Cells only
Microtubule Movement Flagella and cilia made of microtubules Comes off Basal Body Set of 9 triplets Like centriole Extension in a arrangement 2 microtubules in center 9 pairs (doublet) of microtubules surround
Dynein – A Motor Protein Attach between microtubules to cause movement: “walking” If cross-link proteins, microtubules will bend Results in “swishing” movement
Microtubules Transportation ER is limited (short, not far-reaching) Transport materials along cytoskeleton Made of 4 parts 1) Vesicle/Organelle 2) Motor protein 3) Connector molecule (protein complex) 4) Microtubule (tracks) Dynein – moves in Kinesin – moves out
Microfilament “Movement” Fiber network is dynamic and changing Actin microfilaments constantly dissolving and forming to change shape of cell Can allow cell to crawl (like amoeba)
Actin Structures Muscle Fibers Actin + Myosin Amoeboid Movement Pseudopods Cytoplasmic Streaming Actin + Myosin
Small Cellular Extensions Microvilli (singular: Microvillus) Supported by actin (much smaller than flagella/cilia) WHY have these? Increase Surface Area
Intermediate Fibers Actual skeleton Prevents stretching and compression Makes up nuclear lamina, etc. Usually left over when cell dies Cell Overview (short then long)