Chapter 4: The Characteristics of Prokaryotic and Eukaryotic Cells by 7LxUeRH

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									Overview and Review
 Prokaryotic Cells-cells
 lacking a nucleus and
 other membrane-
 enclosed structures
   Belong to either Archaea
    or Bacteria Kingdoms
 Eukaryotic Cells-cells
 with a nucleus and
   Have organelles
Prokaryotic Cells
 Size
    Diameter of 0.5-2.0 μm
    Spherical, Spiral with large Diameters
    Large Surface-to-Volume Ratio
        Spherical Bacteria with 2 μm Diameter, 12 μm2 Surface Area, 4
         μm3 Volume: 3:1
        Eukaryotic Cell with 20 μm Diameter, 1200 μm2 Surface Area,
         4000 μm3 Volume: 0.3:1
        Parts of Cell are close to Surface
Prokaryotic Cells
 Shape
    Three Main Shapes:
       Coccus—spherical bacterium
       Bacillus—rod-like bacterium
       Spiral-shaped bacterium are fitted under the category of
          Vibrio—comma-shaped bacterium

          Spirillium—rigid, wavy-shaped bacterium

          Spirochete—corkscrew-shaped bacterium

   Also Square and Triangular Bacteria Exist
   Pleomorphism—occurrence of bacteria varying in
    form within a single culture under optimal conditions
    3   5

2   4
Prokaryotic Cells
 Arrangement                         Bacilli
    Bacteria form unique                Divide in One Plane
     arrangements                            End-to-End or Side-by-Side
    Cocci                            Spiral Bacteria don’t group
        Division in One Plane in      together
         pairs-- diplo-
        Division in One Plane in
         chains– strepto-
        Division in Two Planes–
        Division in Three Planes–
        Random Division–
Prokaryotic Cells
 Cell Membrane
    Fluid-Mosaic Model
    Hydrophilic and Hydrophobic
 Cytoplasm, Ribosomes, Nucleoid, Endospores,
  Chromatophores(internal membrane structures),
  Inclusions(Granules and Vesicles)
 Flagella(Chemotaxis vs. Phototaxis), Axial Filaments,
  Pili(attach bacteria to surface)
Cell Wall
 Maintains characteristics and protects the cell
 Components
    Peptidoglycan-polymer in cell wall that forms a surrounding
        Fortified with Four Types of Amino Acids
        Gram-Positive Bacteria contain Teichoic acid-furnishes attachment
         sites for bacteriophages and serves as a passage for entering/exiting
    Outer Membrane-layer of lipoproteins next to the Cell Wall
      Composed of Lipopolysaccharides or endotoxins

    Periplasmic Space-gap between Cell Membrane and Cell
        Characteristic of Gram-Negative Bacteria
Cell Wall
Gram-Positive Bacteria             Gram-Negative Bacteria
 Thick layer of Peptidoglycan      10%-20% of Wall is
  (60%-90%) -----20 to 80 nm         Peptidoglycan
  across                            Periplasmic space separates
 Forms a Protoplast when the        wall from membrane
  peptidoglycan is digested.        Form Spheroplasts when the
 Retains the violet-iodine dye      wall is digested
  used for staining---due to        Don’t retain stain b/c of
  wall thickness                     relatively thin walls
    Wall thickness deteriorates
     b/c of damage or aging
Cell Wall
 Additional Information on Cell Walls
    Acid-Fast Bacteria
    L-forms-bacteria strains w/o cell walls
Eukaryotic Cells
 Have more lipids than Prokaryotic Cells
 Diameter of 10 μm
 Review of Components: Plasma Membrane,
  Cytoplasm, Cell Nucleus, Mitochondria, Chloroplasts,
  Ribosomes, Endoplasmic Reticulum, Golgi Apparatus,
  Lysosomes, Peroxisomes, Vacuoles, Cytoskeleton
 Flagella, Cilia, Pseudopodia(Amoeboid Movement),
  Cell Wall
Endosymbiotic Theory
 Organelles of eukaryotic cells may have arose from
  prokaryotic cells that had developed a symbiotic
  relationship with “future”-eukaryotic cells.

   Means one cell lives inside the other

   Many examples of Prokaryotic Cells living inside
    Eukaryotic Cells
 Evidence:
    Mitochondria and Chloroplasts are approx. the same size as
     prokaryotic Cells
    Mitochondria and Chloroplasts have their own DNA
    Organelles have 70S ribosomes---like prokaryotic ribosomes
    Organelle DNA/Ribosomes synthesize protein like bacteria
    Mitochondria and Chloroplasts divide by binary fission,
     independently of the eukaryotic cell cycle
    Double-Membrane Structure of Mitochondria and
     Chloroplasts resembles Gram-negative bacteria’s cell
The Movement of Substances
Across Membranes
Simple Diffusion                Facilitated Diffusion
 Net Movement of Particles      Diffusion down a
  from a region of higher to      concentration gradient and
  lower concentration             across a membrane with the
 Selectively Permeability        assistance of special pores or
  affects which materials can     carrier molecules
  penetrate the membrane         Carry substances in
 Limits Cell Size                proportions to concentrations
The Movement of Substances
Across Membranes
Osmosis                            Active Transport
 Diffusion of Water Molecules      Movement of molecules and
  across a selectively permeable     ions against concentration
  membrane                           gradients from regions of
 Osmotic Pressure-pressure          lower to higher
  required to prevent osmosis        concentrations
  from occurring.
 Isotonic vs. Hypotonic vs.
The Movement of Substances
Across Membranes
Endocytosis                     Exocytosis
 Process in which vesicles      Process by which vesicles
  form by invagination of the     inside a eukaryotic cell fuse
  plasma membrane to move         with the plasma membrane
  substances into eukaryotic      and release their contents
  cells                           from the eukaryotic cell

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