Structure of Prokaryotic Eukaryotic Cells

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					Structure of Prokaryotic &
     Eukaryotic Cells
Review of Prokaryotic & Eukaryotic
              Cells
• Nucleus vs nucleoid
• DNA : circular vs linear, presence of
  histones
• Membranous organelles
• Cell wall-peptidoglycan
• Cell division: binary vs mitosis
• Ribosomes: 70S vs 80S
• Cytoskeleton
                    Shape
• Cocci
  – Diplococci
  – Streptococci
  – Tetrads
  – Sarcinae
  – Staphylococci
                   Bacillus
• Coccobacilli

• Diplobacilli

• Streptobacilli
                    Spiral
• Vibrio-curved rods

• Spirilla-helical & rigid

• Spirochetes-helical & flexible

• Other shapes
• Pleomorphic
             Glycocalyx
• Glycolipids or glycoproteins
• Surrounds cell
• Capsule or slime layer
• Capsule more organized & attached to
  wall
• Advantages of capsule
          Slime Layer(Biofilm)
•   Surrounds cell
•   Loosely organized & not attached
•   Tangled mass of fibers-dextran
•   Attachment to surfaces -S. mutans
•   Shields bacteria from immune defense &
    antibiotics
       Glycocalyx -Eukaryotes
•   Animal cells have one
•   Made of carbohydrates
•   No do not have a cell wall
•   Surround plasma membrane
•   Stabilizes PM
                 Flagella
• Movement
  – Spins like propeller
  – Clockwise or counter clockwise


• Chemotaxis- movement toward or away
              Arrangements
•   Monotrichous: one at end
•   Amphitrichous: both ends
•   Lophotrichous: tuft at end or ends
•   Peritrichous: around the cell
                 Structure
• Composition-protein subunits: flagellin (H
  protein) E. coli H7
  – Chains twisted together with hollow core
  – Helical shaped
  – Filament, hook, basal body
  – Hook
  – Basal body:
                  Flagella
• Basal body

• Classified by flagella protein
             Axial Filament
• Spirochetes
  – Treponema pallidum-syphilis
  – Borrelia burgdorferi-Lyme disease
• Bundle of fibrials within a sheath
• Corkscrew motion
       Movement Eukaryotes
• Flagella & cilia




  – 9+2 arrangement of microtubules


  – Cilia in Paramecium & respiratory cells
     Prokaryote Fimbriae & Pili
• Made of pilin: string of subunits

• Function: attachment

• Few to hundreds
• Fimbrae

• Pili-longer & fewer

• Not in eukaryotes
               Cell Wall
• Function




• Basis of Gram stain
               Composition
• Peptidoglycan
  – Repeating subunits of disaccharides
    • N-acetyl glucosamine (NAG)
    • N-acetyl muramic acid (NAM)
    • Linked alternately in rows
  – Attached by polypeptides
    • Tetrapeptide side chains link NAM subunits
    • Cross bridge of amino acids link tetrapeptides
  – Forms lattice
             Peptidoglycan
• Confers shape & prevents lysis
• Cell growth
  – Autolysins break cross linkages in
    peptidoglycan
  – Transpeptidases seal breaks
  – Penicillin inactivates these enzymes
• Existing cells
  – Treat with lysozyme-tears, saliva etc.
  – Destroys linkages between carbohydrates
      Gram Positive Cell Wall
• Thick layers: 40-80% of dry wt, up to 30
  layers
• Contains teichoic acid
  – Alcohol and phosphate
  – Negative charge

  – Cell growth-prevents lysis
  – Antigenic properties
     Gram Negative Cell Wall
• Few layers of peptidoglycan- 10%
• Outer membrane: bilayer




• Periplasm
                    LPS
• Strong negative charge

• Barrier to some antibiotics

• Outer membrane-endotoxin
  – O polysaccharides
  – Lipid-lipid A
               Gram Stain
• Differential stain dev by Hans Gram 1880s
  – Classifies bacteria into 2 groups
  – Based upon cell wall composition
  – Gram variable stain unevenly



  – Gram non reactive do not stain or stain poorly
             Comparison
• Gram positives
          Gram Negatives

• ETOH disrupts outer layer
• CV-I complex is washed out of thin
  peptidoglycan layer
• Counterstain
          Atypical Cell Walls
• Streptococci

• Mycobacteria

• Mycoplasma
  – PM unique with sterols protect from lysis
            Mycoplasma
• Lack a cell wall so pleomorphic
• Classified with gram positives
• Smallest genome of any bacteria


• Droplet spread-use regular mask
• Why can’t you use penicillin?
        Cell wall of Eukaryotes
•   Simpler than prokaryotes
•   Algae & plants
•   Fungi
•   Yeasts
•   Protozoa

• Animals
          Plasma Membrane
• Thin, fluid structure inside cell wall-viscous
• Proteins

• Phospholipids-2 layers
       Functions of Membrane
•   Selective permeability
•   Passive transport:
•   Active transport:
•   Enzymes break down nutrients
•   Infoldings
    Plasma Membrane of Eukaryotes
•   Phospholipids and proteins
•   Carbohydrates and sterols-cholesterol
•   More rigid than prokaryotic PM
•   Endocytosis



• Exocytosis
    Cytoplasm of Prokaryotes
• 80% water, thick, solutes
• Increase in osmotic pressure on
  membrane
  – Rigid cell wall prevents lysis
• Contains DNA
• Ribosomes
• Inclusion bodies
     Cytoplasm of Eukaryotes
• Cytosol-fluid portion
• Cytoskelton
  – Microfilaments:
  – Microtubules:

  – Intermediate filaments:
• Cytoplasmic streaming
                Ribosomes
•   2 subunits of protein and rRNA
•   70s ribosomes
•   Polyribosomes-chains
•   Protein synthesis



• Eukayotes-80s
               Inclusions
• Polysaccharide granules

• Sulfur granules

• Reserve deposits-volutin (phosphates)
              Endospores
• Unique to bacteria: Clostridium & Bacillus
• Sporulation-formation of spores
               Germination
•   Triggered by damage to coat
•   Enzymes break down endospore
•   Water enters & metabolism begins
•   Not a reproductive structure
     Nuclear Area of Bacteria
• Single, ds DNA chromosome
• Attached to PM at some point
• Nucleoid area, not a nucleus

• Plasmids
                 Nucleus
• Largest structure in cell

  – Nucleoli


• DNA associated with proteins -histones
    Organelles in Eukaryotes
• Unique to eukaryotes
• Membranous structures
  – Endoplasmic reticulum
    • Smooth & rough
  – Golgi complex
  – Lysosomes
  – Mitochondria
  – Cloroplasts
                   ER
• Flattened membranous sacs
• Rough ER-ribosomes attached


• Smooth ER- no ribosomes


• Free ribosomes- proteins don’t need
  processing
            Golgi Complex
• Stacks of membranous sacs
• Receive transport vesicles from ER
• Modify molecules to form glycoproteins,
  glycolipids lipoproteins
• Transported in secretory vesicles to PM or
  to outside cell
              Lysosomes
• Formed from Golgi
  – Contain digestive enzymes: proteases &
    nucleases
  – Break down old parts of cell
  – Breaks down pathogens
            Mitochondria
• Double membrane




• Generation of ATP
              Chloroplasts
• Thylakoids-flattened membranous sacs


• Contain DNA 70s ribosomes
• Stroma thick fluid in center- Calvin cycle
• Generation of ATP & sugars