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 (
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.
Cell Crawling (Cntd.) Functions Embryo formation Immune system Cancer
Cell Movement Mouse Fibroblasts Mouse Melanoma Chick Fibroblasts Fish Epidermis
Video: 15-3, Alberts: Molecular Biology of the Cell. Also at:
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 arrangement. Use dynein for motion. Anchored by a basal body.
Cilia and Flagella ok/cellmove.htm cheng/envs161/Lectur e8/ 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…
h=October&year=2004 Extracellular Matrix Tissue Repair ECM: Recruits cells for tissue remodeling without scarring.
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
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
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.