Chapter 4: The Characteristics of Prokaryotic and
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Transcript Chapter 4: The Characteristics of Prokaryotic and
Overview and Review
Prokaryotic Cells-cells
lacking a nucleus and
other membraneenclosed structures
Belong to either Archaea
or Bacteria Kingdoms
Eukaryotic Cells-cells
with a nucleus and
membrane-enclosed
structures
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
coccobacilli
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
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Prokaryotic Cells
Arrangement
Bacteria form unique
arrangements
Cocci
Division in One Plane in
pairs-- diploDivision in One Plane in
chains– streptoDivision in Two Planes–
tetrads
Division in Three Planes–
sarcinae
Random Division–
staphylo-
Bacilli
Divide in One Plane
End-to-End or Side-by-Side
Spiral Bacteria don’t group
together
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
net
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
ions
Outer Membrane-layer of lipoproteins next to the Cell Wall
Composed of Lipopolysaccharides or endotoxins
Periplasmic Space-gap between Cell Membrane and Cell
Wall
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
across
Forms a Protoplast when the
peptidoglycan is digested.
Retains the violet-iodine dye
used for staining---due to
wall thickness
Peptidoglycan
Periplasmic space separates
wall from membrane
Form Spheroplasts when the
wall is digested
Don’t retain stain b/c of
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
Endosymbiosis
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
membranes
The Movement of Substances
Across Membranes
Simple Diffusion
Facilitated Diffusion
Net Movement of Particles
Diffusion down a
from a region of higher to
lower concentration
Selectively Permeability
affects which materials can
penetrate the membrane
Limits Cell Size
concentration gradient and
across a membrane with the
assistance of special pores or
carrier molecules
Carry substances in
proportions to concentrations
The Movement of Substances
Across Membranes
Osmosis
Active Transport
Diffusion of Water Molecules
Movement of molecules and
across a selectively permeable
membrane
Osmotic Pressure-pressure
required to prevent osmosis
from occurring.
Isotonic vs. Hypotonic vs.
Hypertonic
ions against concentration
gradients from regions of
lower to higher
concentrations
The Movement of Substances
Across Membranes
Endocytosis
Exocytosis
Process in which vesicles
Process by which vesicles
form by invagination of the
plasma membrane to move
substances into eukaryotic
cells
inside a eukaryotic cell fuse
with the plasma membrane
and release their contents
from the eukaryotic cell