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UW-Madison BIOLOGY 151 - Cytoskeleton

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BIO 151 1nd Edition Lecture 7 Outline of Last Lecture II. Endomembrane systema. Traffic patternsb. Exocytosis/endocytosisc. Degradation and recyclingIII. Cytoskeletona. Filament typesOutline of Current Lecture- Cytoskeletono Filament typeso Polarityo Cellular motility- Structural Reinforcemento Intermediate Filamentso Cell wallsCurrent Lecture- Cytoskeleton: provides mutual support  proteins that assemble into long filaments“Building analogy” Filament Diameter Subunits/StructureGirders Microtubules (MT) 25 nm(1nm=1x10-9m)Tubulin/hallow rods2x4’s wood Intermediate filaments (IF)~10nm Many ei. KeratinWires Microfilaments (MF) ~7nm* Actin/2 twisted These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.strands*membrane bilayer: 6-8nm- MT’s: vesicle movement; cell mobility in terms of cilia and flagella; role in chromosome separation (mitosis)- MF’s: role in muscle action; cytokinesis (cell division); important in amoeboid movement; involved in cytoplasmic streamingo Features of function in cytoskeleton why important Large protein polymers with inherent polarity Interact with cellular motors- Polarity comes from the fact that subunits are polar  means they have sidedness to them  polymers also have sidedness to themo Ei. MT’s Subunits: tubulin dimers (2 proteins=building block) 2 molecules/2 subunits come together to make tubulin dimer *Quaternary Structure - Stable complex: beta and alpha To build filament: add complex together in alpha and beta spiral- Interact with neighbors  spiral action- Polar  sidednesso + end adds blocks more easily; growing end; beta sideo – end not a lot of action; non growing end; alpha side In animal cell, minus ends will be in middle; positive, growing side will be on the end- Not charged, ends are just to show growing side- Centrosome: central body; example of MT organizing centers- MTOC: site where MT assembly starts; beta and alpha are like signposts- Cell Mobility (ei. In muscles allows us to walk; can have large effects on cyto level)o Always has two elements Cytoskeletal: element w/ polarity (MT’s or MF’s (either built on)) Cellular Motor: usually attached to a cargo - Ei. vesicle could be a cargo- Cellular motors: 1 direction, 1 speed (cannot go back and forth)o Direction: +end-directed motors; - ended directed motor Motors work in pairs- Examples of cell motility systemso Muscle Action Filament: MF (actin) Motor: Myosin (muscle related) Motors heads stuck out and can touch actin; actin will pull together; contracted muscle shorten length; relax muscle; only works in 1 directiono Cilia and Flagella Flagella: single cell has long tail (ei. sperm cell) Cilia: cell with short processes (ei. Paramecium) Have cone of microtubules (MT)  a double Mt’s; 2 central single MT’s- Filament: MT’s (tubulin)- Motor: dynesino Result: traveling wave in flagella; power stroke in cilia- Other structural elements of importanceo Intermediate filaments (part of cytoskeleton): strengthening role; gives resistance to mechanical stress; important in animal sills (bc they lack cell walls)o Cell walls (plants, fungi): not cytoskeleton; external support feature/elements; outside plasma membrane;  Major component (in plants): cellulose (B-1 made at cell surface, 4 linked glucose) Other polysaccharides (made in golgi) glycoproteins (made in ER, modified in


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