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)