Cytoskeleton and Extracellular Matrix

1. Cytoskeleton and Extracellular Matrix Block 5 Erik Kessler, Michael O’Brien, Bryan Richman

2. Structure: • Meshwork of fine fibers within the cell • Made up of three types of fibers • Microfilaments, Intermediate Filaments, and Microtubules • Gives the cell some structural support • Plays a role in cell movement • Movement of organelles, and cell itself • Needed for muscle contraction • Regulates cellular activity Cytoskeleton Function: More in textbook pg.64

3. Globular proteins are hydrophilic Structure: • Solid rod made mostly of the globular protein actin • Double twisted chain that is 5-9 nm in diameter • Changes shape by moving subunits from the end to the front • This can change cell shape and make it move ex. Amoeba • Can interact with myosin to contract muscles • Allows a dividing cell (cytokinesis) to pinch off into two cells Microfilaments Function: More in textbook pg.64

4. Fibrous proteins are hydrophobic Structure: • Rope-like structure • Made of fibrous protein • 8-11 nm in diameter • Made of subunits • monomer - rod connecting amino head to carboxyl tail • dimer - two monomers combine • tetramer - two dimers combined • tetramers combine into sheets which role up into its rope shape Intermediate Filaments More in textbook pg.64

5. Function: • Keep organelles in place and holds the cell structure • ex. Hold nucleus in place • Can assemble and disassemble through phosphorylation with serine • Can bind with different proteins to improve stability or create attachment sites for protein assemblies • ex. actin filaments (microfilaments), microtubules • Help to attach chromosomes to nuclear membrane Intermediate Filaments More in textbook pg.64

6. Structure: • Made of globular proteins • 20-25 nm in diameter • Act as track for organelle movement through cytoplasm • ex. lysosomes move along microtubules to reach vacuole, also support and move cilia and flagella • Guide chromosomes when cells divide • Move by adding tubulin to one end and losing them on the other Microtubules Function: More in textbook pg.64 And watch the cilia and flagella PowerPoint for more on their function

7. Structure: • Sticky layer of glycoproteins • Made of: collagen and elastin (structural proteins), fibrillin and laminin (specialized proteins) • Holds animal cells together in tissues • Protects and supports cells • Regulates cell behavior • Gives strength, protection, and support to soft parts of the body (cartilage, etc.) Extracellular Matrix Function: More in textbook pg.66

8. Function: • Adjacent cells in animal tissues are connected by cell junctions • Regulates what comes into the cell • Tight Junction: Binds cells together and forms a leak proof sheet • Prevents passage of molecules through the space between cells • Anchoring Junction: Attach cells to each other while still allowing material to pass in the area between the cells • Communicating Junction: Channels allowing water, small molecules, and ions to flow between adjacent cells- cells can communicate with electrical/ chemical signals Cell Junctions Types: More in textbook pg.66

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