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PROKARYOTIC CELLS and EUKARYOTIC

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PROKARYOTIC CELLS and EUKARYOTIC Powered By Docstoc
					PROKARYOTIC CELLS
       and
 EUKARYOTIC CELLS
CELLS


 The microscopic study of cells
     reveals 2 types of cells:
   prokaryotic and eukaryotic.
EUKARYOTIC CELLS
Eukaryotic cells are more complex
  than prokaryotic cells. They are
     they larger and have many
    organelles including a nuclear
     envelope. This results in a
  separation of their chromosomes
 (chromatin) from their cytoplasm.
PROKARYOTIC CELLS
 Prokaryotic cells are generally much
   smaller than most eukaryotic cells.
    This allows these cells to take in
 nutrients and excrete waste products
 easier, which results in a greater rate
  of multiplication. These cells do not
   have a nuclear envelope and have a
     limited number of organelles.
       MORPHOLOGY OF
       PROKARYOTIC CELLS
Prokaryotes
exhibit a variety of
shapes
     Most common
        Coccus
                Spherical
          Bacillus
                Rod or cylinder
                 shaped
       MORPHOLOGY OF
       PROKARYOTIC CELLS
Prokaryotes exhibit a
variety of shapes
      Other shapes
           Coccobacillus
                 Short round rod
           Vibrio
                 Curved rod
           Spirillum
                 Spiral shaped
           Spirochete
                 Helical shape
           Pleomorphic
                 Bacteria able to
                  vary shape
        MORPHOLOGY OF
        PROKARYOTIC CELLS
Division along a single
plane may result in
pairs or chains of cells
      Pairs = diplococci
           Example: Neisseria
            gonorrhoeae
      Chains = streptococci
           Example: species of
            Streptococcus
  MORPHOLOGY OF
  PROKARYOTIC CELLS

Division along
several random
planes form
clusters
     Example: species of
      Staphylococcus
       MORPHOLOGY OF
       PROKARYOTIC CELLS

Division along two or
three perpendicular
planes form cubical
packets
     Example: Sarcina
      genus
PROKARYOTIC CELL
PROKARYOTIC CELLS
CELL APPENDAGES
FLAGELLA
Some bacteria have protein
 appendages
     Not essential for life
        Aid    in survival in certain environments
     They include
        Flagella

        Pili
            FLAGELLA
Flagella
      Long protein structure
      Responsible for motility
           Use propeller like
            movements to push
            bacteria
           Can rotate more
            than 100,00
            revolutions/minute
                 82 mile/hour
      Some important in
       bacterial pathogenesis
FLAGELLA
           Flagella structure has
           three basic parts
                 Filament
                     Extends to exterior

                     Made of proteins called
                      flagellin
                 Hook
                     Curved sheath

                     Connects filament to
                      cell
                 Basal body
                     Anchors flagellum into
                      cell wall and membrane
      FLAGELLAR
      ARRANGEMENTS

1. Monotrichous – single flagellum at one end
2. Lophotrichous – small bunches arising from
    one end of cell
3. Amphitrichous – flagella at both ends of cell
4. Peritrichous – flagella dispersed over
    surface of cell, slowest
       FLAGELLA
Bacteria use flagella
for motility
      Motile through sensing
       chemicals
           Chemotaxis
      If chemical compound
       is nutrient
           Acts as attractant
      If compound is toxic
           Acts as repellent
Flagella rotation
responsible for run
and tumble movement
of bacteria
       PILI
Rigid tubular
structure made of
pilin protein

Found only in Gram
negative cells

Functions
      Sexual pili—joins
       bacterial cells for DNA
       transfer (conjugation)
      Common pili—adhesion
    FIMBRAE

Fine hairlike
bristles from the
cell surface

Function in
adhesion to other
cells and surfaces
CELL ENVELOPE
      GLYCOCALYX

Coating of molecules external to the cell wall,
    made of sugars and/or proteins
2 types
      1.   slime layer - loosely organized and attached
      2.   capsule – highly organized, tightly attached
Functions
     attachment
     inhibits killing by white blood cells
     receptor
2 TYPES OF GLYCOCALYX
      BIOFILM
Dental Plaque
     A polysaccharide-
      encased mass of
      bacteria coating the
      surface of a tooth
     Streptococcus mutans
      uses sucrose to
      synthesize a biofilm
     Other bacteria can then
      adhere to the layer
CELL WALL
Bacterial cell wall
     Rigid structure
     Surrounds cytoplasmic membrane
     Determines shape of bacteria
     Holds cell together
     Prevents cell from bursting
     Unique chemical structure
        Distinguishes   Gram positive from Gram-
        negative
GRAM POSITIVE   GRAM NEGATIVE
       GRAM POSITIVE WALL
Rigidity of cell wall is due to
peptidoglycan (PTG)
      Compound found only in bacteria
Basic structure of
peptidoglycan
      Alternating series of two subunits
         N-acetylglucosamine (NAG)
         N-acetylmuramic acid (NAM)
      Joined subunits form glycan chain
         Glycan chains held together by
           string of four amino acids
               Tetrapeptide chain
GRAM POSITIVE WALL
        Gram positive cell wall
              Relatively thick layer of
               peptidoglycan
                   As many as 30
                        Regardless of thickness,
                         peptidoglycan is permeable to
                         numerous substances
              Teichoic acid component of
               peptidoglycan; composed of
               glycerol and phosphate
              Lipoteucholic acid is attached to
               the lipids of cytoplasmic
               membrane
                  Gives cell negative charge
GRAM POSITIVE WALL
GRAM POSITIVE   GRAM NEGATIVE
            GRAM NEGATIVE WALL
Gram-negative cell wall
      More complex than Gram+
      Only contains thin layer of
       peptidoglycan
           Peptidoglycan sandwiched
            between outer membrane and
            cytoplasmic membrane
           Region between outer
            membrane and cytoplasmic
            membrane is called periplasm
            or periplasmic space
                 Gel-like area
                 Most secreted proteins
                  contained here
         GRAM NEGATIVE WALL
Outer membrane
   Connected to the peptidoglycan layer by lipoproteins
   Constructed of lipid bilayer
        Much   like cytoplasmic membrane but outer layer made
         of lipopolysaccharides and phospholipids
        Outer membrane also called the lipopolysaccharide
         layer or LPS layer
     LPS severs as barrier to a large number of molecules
        Small   molecules or ions pass through channels called
         porins
        Specific channel proteins are present
       GRAM NEGATIVE WALL

O-specific polysaccharide chain
     Directed away from membrane
        Opposite location of Lipid A

     Used to identify certain species or strains
        E. coli O157:H7 refers to specific O-side chain

Lipid A
     Portion that anchors LPS molecule in lipid bilayer
     Plays role in recognition of infection
        Molecule present with Gram negative infection of
         bloodstream--endotoxin
GRAM NEGATIVE WALL
CELL WALL
Peptidoglycan layer as a target
     Many antimicrobial interfere with the
      synthesis of peptidoglycans or alter its
      structural integrity
     Examples include
        Penicillin

        Lysozyme
CELL WALL
Penicillin
     Binds proteins involved in cell wall synthesis
          Prevents cross-linking of glycan chains by
           tetrapeptides
     More effective against Gram positive
      bacterium
        Due to increased concentration of peptidoglycans
        Penicillin derivatives produced to protect against
         Gram negatives
CELL WALL
Lysozymes
     Produced in many body fluids including
      tears and saliva
     Breaks bond linking NAG and NAM
        Destroys   structural integrity of cell wall
     Enzyme often used in laboratory to remove
      peptidoglycan layer from bacteria
        Produces protoplast in G+ bacteria
        Produces spheroplast in G- bacteria
CELL WALL
Differences in cell wall account for
differences in staining
Characteristics:
     Gram-positive bacterium retain crystal violet-
      iodine complex of Gram stain
     Gram-negative bacterium lose crystal violet-
      iodine complex
CELL WALL
Some bacterium naturally lack cell wall
     Mycoplasma
        Bacterium causes mild pneumonia

        Have no cell wall
               Antimicrobial directed towards cell wall ineffective
          Sterols in membrane account for strength of
           membrane
CYTOPLASMIC MEMBRANE

Cell (Cytoplasmic) membrane
     Delicate thin fluid structure
     Surrounds cytoplasm of cell
     Defines boundary
     Serves as a semi permeable barrier
               between cell and external
        Barrier
        environment
CELL MEMBRANE
        Structure is a lipid
        bilayer with embedded
        proteins
             Bilayer consists of two
              opposing layers
                Layer composed of
                  phospholipids
                      Each contains a
                       hydrophilic phosphate
                       head and hydrophobic
                       fatty acid tail
               CELL MEMBRANE
Membrane is embedded
with numerous protein
     More that 200 different proteins
     Proteins function as receptors,
      channels proteins, and transport
      proteins
     Provides mechanism to sense
      surroundings
     Proteins are not stationary
        Constantly changing position
              Called fluid mosaic model
CELL MEMBRANE
Cytoplasmic membrane is
 selectively permeable
     Determines which molecules pass into or
      out of cell
        Few   molecules pass through freely
Molecules pass through membrane
 via simple diffusion or transport
 mechanisms that may require
 carrier proteins and energy
CYTOPLASM
CYTOPLASM

Dense gelatinous solution of sugars,
amino acids, & salts

70-80% water

Serves as solvent for materials
used in all cell functions
STRUCTURES WITHIN
CYTOPLASM
Bacterial cells have variety of internal
  structures
Some structures are essential for life
     Chromosome
     Ribosome
Others are optional and can confer
 selective advantage
     Plasmid
     Storage granules
     Endospores
               INTERNAL STRUCTURES
Chromosome
      Resides in cytoplasm
         In nucleoid space
      Typically single chromosome: protein and
       DNA
      Circular double-stranded molecule
      Contains all genetic information
Plasmid
      Circular DNA molecule
           Generally 0.1% to 10% size of
            chromosome
      Extrachromosomal
           Independently replicating
      Encode characteristic
           Potentially enhances survival
                 Antimicrobial resistance
                 Tolerance to toxic metals
           INTERNAL STRUCTURE
Ribosome
     Involved in protein synthesis
     Composed of large and
      small subunits
          Units made of protein 40%
           and ribosomal RNA 60%
     Prokaryotic ribosomal
      subunits
          Large = 30S
          Small = 50S
     Small than eukaryotic
      ribosomes
          Difference often used as
           target for antimicrobials
            INTERNAL STRUCTURES
Storage granules
     Accumulation of polymers
        Synthesized from excess
         nutrient
              Example = glycogen
                  Excess glucose in cell
                   is stored in glycogen
                   granules
Gas vesicles
     Small protein compartments
        Provides buoyancy to cell
        Regulating vesicles allows
         organisms to reach ideal
         position in environment
             INTERNAL STRUCTURES
Endospores
     Dormant cell types
          Produced through sporulation
          Theoretically remain dormant for
           100 years
     Resistant to damaging conditions
          Heat, desiccation, chemicals and
           UV light
     Vegetative cell produced through
      germination
          Germination occurs after
           exposure to heat or chemicals
          Germination not a source of        Common bacteria genus that
           reproduction                       produce endospores include
                                              Clostridium and Bacillus
                 INTERNAL STRUCTURES
Endospore formation
      Complex, ordered sequence
Bacteria sense starvation and begin
sporulation
      Growth stops
      DNA duplicated
      Cell splits
         Cell splits unevenly
                Larger component engulfs small component,
                 produces forespore within mother cell
                    Forespore enclosed by two membranes
      Forespore becomes core
      Peptidoglycan between membranes forms
       core wall and cortex
      Mother cell proteins produce spore coat
      Mother cell degrades and releases endospore

				
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