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

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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
3
1
2
4
5
Prokaryotic Cells
 Arrangement
 Bacteria form unique
arrangements
 Cocci


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
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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