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Bio 178 Lecture 10 Cell Structure (Cntd.) Copyright: E.G. Platzer Reading • Chapters 5 & 6 Quiz Material • Questions on P 104 & 124 • Chapters 5 & 6 Quiz on Text Website (www.mhhe.com/raven7) Outline • Eukaryotic Cells (Cntd): 1. Cell Movement 2. Extracellular matrix 3. Specialized Plant Cell Features • Biological Membranes Myosin and Actin Video Alberts et al.: Molecular Biology of the Cell, 16.8 Cell Movement Involves actin filaments and microtubules. Crawling Mechanism • Actin polymerizes to form protrusions that attach to substratum & pull cytoplasm forward. • Involves myosin motors. http://www.bio.umass.edu/vidali/web/cell_motil/sept_26_long.htm Cell Crawling (Cntd.) Functions • Embryo formation • Immune system • Cancer Cell Movement Mouse Fibroblasts Mouse Melanoma Chick Fibroblasts Fish Epidermis http://cellix.imolbio.oeaw.ac.at/Videotour/video_tour_2.html Video: 15-3, Alberts: Molecular Biology of the Cell. Also at: http://www.biochemweb.org/fenteany/research/cell_migration/neutrophil.html Cell Movement (Cntd.) Swimming Mechanism • Cilia - Short projections that beat with a whip-like motion, eg. Vertebrate respiratory tract, Paramecium. • Flagella - Longer than cilia. Undulating motion, eg. Sperm. Structure • Microtubules in 9 + 2 arrangement. • Use dynein for motion. • Anchored by a basal body. Cilia and Flagella http://ic.ucsc.edu/~wx cheng/envs161/Lectur e8/ http://www.tmd.ac.jp/artsci/biol/textbo ok/cellmove.htm http://www.vetanatomists.org/LIBRARY/tn mrepro3.htm Structure of the ECM of Animals Extracellular Matrix (ECM) Description • Acellular part of a tissue. • Composed mainly of fibrous proteins and glycoproteins in animals. Attachment to Cell • Integrins (transmembrane proteins) anchor intracellularly to the cytoskeleton and extracellularly to fibronectin. • Fibronectin connects to the ECM. ECM (Cntd.) Functions • Scaffold for tissue stabilization • Regulation of cell behavior (eg. migration, development, survival, proliferation, shape, function) Examples Cartilage, bone, cornea… Extracellular Matrix Tissue Repair ECM: Recruits cells for tissue remodeling without scarring. http://www.vanaqua.org/aquanew/archive.php?show=month&mont h=October&year=2004 Specialized Structures of Plant Cells Vacuoles Structure Membrane bound compartment that contains water, organic compounds, inorganic ions, and pigments. Functions Many, including storage, increased cell surface area, and growth. Plant Cell Vacuole Plant Cell Walls Specialized Structures of Plant Cells Cell Wall Structure • Cellulose • Primary cell walls produced first, followed by middle lamella between the cells. • Secondary cell walls laid down on the cellular side of the primary cell wall in some plant cells. The Fluid Mosaic model Davson-Danielli Model (1935) “Phospholipid bilayer sandwiched between 2 globular protein layers”. But…membrane proteins were known to have large hydrophobic regions… Singer and Nicholson (1972) “The proteins span the membrane with the polar regions on the outside and the non-polar regions on the inside”. The Fluid Mosaic Model The Fluid Mosaic Model Description • Membrane is a mosaic of protein and lipid. • Membrane is fluid - proteins and lipids move within it. Fundamental Components of All Cell Membranes • Lipid: Mainly phospholipid and cholesterol. • Protein • Carbohydrate Effect of Cholesterol on Membrane Fluidity High Temperatures Reduces membrane fluidity by interfering with phospholipid mobility. Low Temperatures Increases membrane fluidity by preventing fatty acid tail interactions. Membrane Proteins Functions • Transportation • Enzymes • Receptors • Recognition • Adhesion • Anchoring Functions of Membrane Proteins Membrane Proteins 2 types of membrane protein: Peripheral • Do not extend through the membrane • Attached via non-covalent interactions with anchoring molecules. Easily removed. Integral • Protein held tightly in membrane. Can only be removed by disrupting the bilayer. • Includes transmembrane proteins and proteins anchored in the bilayer by lipid groups. Transmembrane Proteins Transmembrane Proteins 1. Single-Pass Transmembrane Proteins Protein passes through membrane once - one non-polar region. 2. Multiple-Pass Transmembrane Proteins Protein passes through membrane several times using helices Channel Example • Bacteriorhodopsin - 7 pass protein Channel for protons to pass during photosynthesis.