Download E. coli

• Functional Anatomy of Prokaryotic
and Eukaryotic Cells
2008
Prokaryotic Cells
• Comparing Prokaryotic and Eukaryotic Cells
• Prokaryote comes from the Greek words for
prenucleus.
• Eukaryote comes from the Greek words for
true nucleus.
2008
Prokaryote
Eukaryote
• One circular
chromosome, not in
a membrane
• Paired
chromosomes, in
nuclear membrane
• No histones
• Histones
• No organelles
• Organelles
• Peptidoglycan cell
walls
• Polysaccharide cell
walls
• Binary fission
• Mitotic spindle
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• Average size: 0.2 -1.0 µm  2 - 8 µm
• Basic shapes:
2008
• Unusual shapes
• Star-shaped Stella
• Square Haloarcula
• Most bacteria are monomorphic
• A few are pleomorphic
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Figure 4.5
Arrangements
• Pairs: diplococci,
diplobacilli
• Clusters:
staphylococci
• Chains:
streptococci,
streptobacilli
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Glycocalyx
• Outside cell wall
• Usually sticky
• A capsule is neatly
organized
• A slime layer is
unorganized & loose
• Extracellular
polysaccharide
allows cell to attach
• Capsules prevent
phagocytosis
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Figure 4.6a, b
Flagella
• Outside cell wall
• Made of chains of
flagellin
• Attached to a protein
hook
• Anchored to the wall
and membrane by
the basal body
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Figure 4.8
Flagella Arrangement
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Figure 4.7
Flagella arrangement flash animation
2008
2008
Figure 4.8
Flagella structure flash animation
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Motile Cells
• Rotate flagella to run or tumble
• Move toward or away from stimuli (taxis)
• Flagella proteins are H antigens
(e.g., E. coli O157:H7)
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Motile Cells
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Figure 4.9
Axial Filaments
• Endoflagella
• In spirochetes
• Anchored at one end
of a cell
• Rotation causes cell
to move
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Figure 4.10a
Motility flash animation
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• Fimbriae allow
attachment
• Pili are used to
transfer DNA from
one cell to another
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Figure 4.11
Cell Wall
• Prevents osmotic lysis
• Made of peptidoglycan (in bacteria)
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Figure 4.6a, b
Peptidoglycan
• Polymer of disaccharide
N-acetylglucosamine (NAG) & N-acetylmuramic acid
(NAM)
• Linked by polypeptides
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Figure 4.13a
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Figure 4.13b, c
Gram-positive cell walls
Gram-negative cell walls
• Thick peptidoglycan
• Teichoic acids
• In acid-fast cells,
contains mycolic
acid
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• Thin peptidoglycan
• No teichoic acids
• Outer membrane
Gram-Positive cell walls
• Teichoic acids:
• Lipoteichoic acid links to plasma membrane
• Wall teichoic acid links to peptidoglycan
• May regulate movement of cations
• Polysaccharides provide antigenic variation
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Figure 4.13b
Gram-Negative Outer Membrane
• Lipopolysaccharides, lipoproteins, phospholipids.
• Forms the periplasm between the outer membrane and
the plasma membrane.
• Protection from phagocytes, complement, antibiotics.
• O polysaccharide antigen, e.g., E. coli O157:H7.
• Lipid A is an endotoxin.
• Porins (proteins) form channels through membrane
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Gram-Negative Outer Membrane
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Figure 4.13c
Gram Stain Mechanism
• Crystal violet-iodine crystals form in cell
• Gram-positive
• Alcohol dehydrates peptidoglycan
• CV-I crystals do not leave
• Gram-negative
• Alcohol dissolves outer membrane and leaves holes
in peptidoglycan
• CV-I washes out
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Atypical Cell Walls
• Mycoplasmas
• Lack cell walls
• Sterols in plasma membrane
• Archaea
• Wall-less, or
• Walls of pseudomurein (lack NAM and D amino
acids)
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Damage to Cell Walls
• Lysozyme digests disaccharide in peptidoglycan.
• Penicillin inhibits peptide bridges in peptidoglycan.
• Protoplast is a wall-less cell.
• Spheroplast is a wall-less Gram-positive cell.
• L forms are wall-less cells that swell into irregular
shapes.
• Protoplasts and spheroplasts are susceptible to
osmotic lysis.
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Plasma Membrane
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Figure 4.14a
Plasma Membrane
• Phospholipid bilayer
• Peripheral proteins
• Integral proteins
• Transmembrane proteins
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Figure 4.14b
Fluid Mosaic Model
• Membrane is as viscous
as olive oil.
• Proteins move to function
• Phospholipids rotate and
move laterally
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Figure 4.14b
Plasma Membrane
• Selective permeability allows passage of some
molecules
• Enzymes for ATP production
• Photosynthetic pigments on foldings called
chromatophores or thylakoids
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Plasma Membrane
• Damage to the membrane by alcohols, quaternary
ammonium (detergents) and polymyxin antibiotics
causes leakage of cell contents.
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Movement Across Membranes
• Simple diffusion: Movement of a solute from an area
of high concentration to an area of low concentration.
• Facilitative diffusion: Solute combines with a
transporter protein in the membrane.
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Movement Across Membranes
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Figure 4.17
Movement Across Membranes
• Osmosis
• Movement of water
across a selectively
permeable membrane
from an area of high
water concentration to
an area of lower water.
• Osmotic pressure
• The pressure needed to
stop the movement of
water across the
membrane.
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Figure 4.18a
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Figure 4.18c-e
Movement Across Membranes
• Active transport of substances requires a transporter
protein and ATP.
• Group translocation of substances requires a
transporter protein and PEP.
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Cytoplasm
• Cytoplasm is the substance inside the plasma
membrane
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Figure 4.6a, b
Nuclear Area
• Nuclear area (nucleoid)
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Figure 4.6a, b
Ribosomes
Figure 4.6a
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Ribosomes
Figure 4.19
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Inclusions
• Metachromatic granules
(volutin)
•Phosphate reserves
• Polysaccharide granules
•Energy reserves
• Lipid inclusions
•Energy reserves
• Sulfur granules
•Energy reserves
• Carboxysomes
•Ribulose 1,5diphosphate carboxylase
for CO2 fixation
• Gas vacuoles
•Protein covered cylinders
• Magnetosomes
•Iron oxide
(destroys H2O2)
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Endospores
• Resting cells
• Resistant to desiccation, heat, chemicals
• Bacillus, Clostridium
• Sporulation: Endospore formation
• Germination: Return to vegetative state
2008
2008
Figure 4.21a
Eukaryotic Cells
• Comparing Prokaryotic and Eukaryotic Cells
• Prokaryote comes from the Greek words for
prenucleus.
• Eukaryote comes from the Greek words for
true nucleus.
2008
2008
Figure 4.22a
Flagella and Cilia
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Figure 4.23a, b
• Microtubules
• Tubulin
• 9 pairs + 2 arrangements
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Figure 4.23c
Cell Wall
• Cell wall
• Plants, algae, fungi
• Carbohydrates
• Cellulose, chitin, glucan, mannan
• Glycocalyx
• Carbohydrates extending from animal plasma
membrane
• Bonded to proteins and lipids in membrane
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Plasma Membrane
• Phospholipid bilayer
• Peripheral proteins
• Integral proteins
• Transmembrane proteins
• Sterols
• Glycocalyx carbohydrates
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Plasma Membrane
• Selective permeability allows passage of some
molecules
• Simple diffusion
• Facilitative diffusion
• Osmosis
• Active transport
• Endocytosis
• Phagocytosis: Pseudopods extend and engulf
particles
• Pinocytosis: Membrane folds inward bringing in fluid
and dissolved substances
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Eukaryotic Cell
• Cytoplasm
membrane
Substance inside plasma
and outside nucleus
• Cytosol
Fluid portion of cytoplasm
• Cytoskeleton
Microfilaments,
intermediate filaments,
microtubules
• Cytoplasmic streaming
Movement of cytoplasm
throughout cells
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Organelles
• Membrane-bound:
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• Nucleus
Contains chromosomes
• ER
Transport network
• Golgi complex
Membrane formation and
secretion
• Lysosome
Digestive enzymes
• Vacuole
Brings food into cells and
provides support
• Mitochondrion
Cellular respiration
• Chloroplast
Photosynthesis
• Peroxisome
Oxidation of fatty acids;
destroys H2O2
Eukaryotic Cell
• Not membrane-bound:
• Ribosome
Protein synthesis
• Centrosome
Consists of protein fibers and
centrioles
• Centriole
Mitotic spindle formation
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Nucleus
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Figure 4.24
Endoplasmic Reticulum
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Figure 4.25
Ribosomes
• 80S
• Membrane-bound
Attached to ER
• Free
In cytoplasm
• 70S
• In chloroplasts and mitochondria
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Golgi Complex
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Figure 4.26
Lysosomes
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Figure 4.22b
Vacuoles
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Figure 4.22b
Mitochondrion
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Figure 4.27
Chloroplast
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Figure 4.28
Endosymbiotic Theory
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Figure 10.2