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Prokaryotic and Eukaryotic Cells

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Title: Prokaryotic and Eukaryotic Cells


1
Prokaryotic and Eukaryotic Cells
  • Chapter 4

2
Structure Function
  • Linkage of Structure function operates at all
    levels
  • NS acts by changing structures to improve
    function
  • Useful ones persist, less useful improve
  • Useless ones are eventually lost

3
Living Organisms
  • All organisms except Viruses are cellular
  • There is and enormous diversity
  • Only Two fundamental types

4
Fundamental Cell Types
  • Prokaryotic Domains Bacteria Archaea
  • Eukaryotic Animals, plants, protozoa, fungi
    algae
  • Differences important from the scientific human
    health standpoint

5
Prokaryotes vs. Eukaryotes
  • Structural Difference
  • Chemical Difference
  • Size Difference

6
Structural Difference
  • Prokaryotes
  • Have organelles but are not membrane bound
  • Have irregular area containing DNA
  • Eukaryotes
  • Membrane bound organelles
  • Defined nucleus

7
Chemical Difference
  • Prokaryotes
  • Cell Wall composed of peptidoglycan
  • Eukaryotes
  • Do not contain peptidoglycan in their cell walls

8
Size Difference
  • Prokaryotes
  • High surface area relative to volume- easier to
    take in nutrients and excrete wastes
  • multiply rapidly
  • Eukaryotes
  • About 10x larger than prokaryotes

9
  • As a cell increases in size its volume increases
    faster than its surface area.
  • Smaller objects have a greater ratio of surface
    area to volume.

10
Prokaryote Cell Structure
11
The Bacterial Cell Structure
  • The Envelope Capsule
  • Pili Flagella
  • Cytoplasm Inclusions

12
The Envelope Capsule
  • The bacterial envelope can be a three layered
    structure
  • Outer Membrane
  • Cell Wall
  • Cytoplasmic Membrane
  • A capsule may or may not surround the envelope

13
The Envelope
  • Gram negative bacteria contain all 3 layers
  • Have an extra compartment between the OM the CM
    ? periplasm
  • Gram positive bacteria lack the OM
  • Mycoplasma lack OM CW

14
Bacterial Envelopes
15
Outer Membrane
  • Only Gram negatives have an OM
  • Composed of a lipid bilayer
  • Inner layer ? phospholipids
  • Outer layer ? lipopolysacchride (LPS)
  • Lipid A
  • O-specific side chain
  • Core polysaccharide
  • LPS also known as endotoxin

16
Lipopolysaccharide
  • Lipid A ? hydrophobic
  • Polysaccharide ? hydrophilic
  • Act as barriers to both polar nonpolar
    substances
  • Only water and a few gases can cross the lipid
    part of the OM
  • Other molecules pass through pores in the OM
  • Pores formed by proteins ? Porin

17
Lipopolysaccharide
  • Held to the envelope by lipoprotein
  • Bonded to the cell wall on one end, other end
    carries lipid that is inserted into the inner
    surface
  • Most important function is protection
  • Makes Gm (-) bacteria more resistant to
    antibiotics
  • Ex rifampin equally inhibits RNA pol. But in Gm
    (-) cant reach target

18
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19
Periplasmic Space
  • In gram (-) lies between the OM and the
    cytoplasmic membrane
  • In gram() lies between the CW and the
    cytoplasmic membrane
  • Contains water, nutrients and substances secreted
    by the cell, such as enzymes and proteins ?
    transport

20
Cell Wall
  • Prokaryotic Cell Walls
  • Provides structure and shape
  • Protects cell from osmotic forces
  • Assists cells in attaching to other cells or
    eluding anti-microbial drugs
  • Animal Cells ? Do not have cell walls
  • Bacterial Cells ? Can target cell wall with
    antibiotics

21
Bacterial Cell Walls
  • Most have cell walls composed of peptidoglycan.
    Few lack a cell wall.
  • Peptidoglycan ? protein polysaccharide, also
    called Murein
  • Peptidoglycan ? form long chains of alternating
    sugars, NAG and NAM
  • NAG and NAM ? held together by protein chains

22
Bacterial Cell Walls
  • Chains of NAG and NAM are attached to other
    chains by tetrapeptide cross bridges
  • Tetrapeptide cross bridges ? two amino acids are
    L-isomers and two are D-isomers
  • Glycan and peptide linked form a mesh-like
    structure

23
Bacterial Cell Walls
  • Two basic types
  • Gram Positive
  • Gram Negative

24
Gram Positive Cell Walls
  • Relatively thick layer of peptidoglycan
  • Contains unique polysaccharides called techoic
    acid
  • Techoic Acid ? Glycerol or Ribitol linked to a
    phosphate group
  • Techoic Acid ? penetrates the multi-layer cell
    wall, making it stronger

25
Gram Negative Cell Walls
  • Have a only a thin layer of peptidoglycan
  • Peptidoglycan mesh is only one layer thick

26
Cell Shape
  • Peptidoglycan confers shape
  • Bacteria come in many sizes , shapes
    arrangements

27
Cocci
28
Rods
29
Comma Spirals
30
Other Shapes
31
Turgor Pressure
  • Osmotic pressure within the cell
  • Approx. 350 lbs/sq in
  • Cell must be protected
  • Cell ? inside highly conc.? unprotected? water
    enters? cell bursts

32
Autolysins Transpeptidases
  • Bacterial cells to increase in size, the
    peptidoglycan has to increase
  • Autolysin breaks the cross bridges
  • Transpetidases reseals by adding new monomers
  • Peptidoglycan increases in size
  • Highly regulated precise process
  • Penicillin/antibiotics inactivate peptidase

33
Mycoplasma, L-Forms and Spheroplasts
  • Mycoplasma ? no cell walls, CM is strengthened by
    sterols
  • L-Forms ? wall-less strains of certain bacteria,
    can return to original form
  • Spheroplasts ? bacteria that have lost cell wall

34
Cytoplasmic Membrane
  • Membrane that encloses cytoplasm
  • Also called a plasma membrane
  • In prokaryotes eukaryotes, the membranes are
    quite similar
  • Called a unit membrane

35
Unit Membrane
  • Phospholipid bilayer
  • Hydrophilic head ? sticks out on both sides
  • Hydrophobic tail ? 2 Fatty Acids, facing each
    other
  • Bilayer studded with proteins ? Carrier or
    transporter proteins ½ the dry weight of the CM
  • Proteins can move with in the membrane ? Fluid
    Mosiac model
  • Bacteria have energy-generating proteins

36
Fluid Mosiac Model
37
Movement Across Membranes
  • Osmosis
  • Facilitated diffusion
  • Active transport
  • Group translocation
  • Engulfment

38
Movement Across Membranes
39
Exocytosis Endocytosis
40
Capsule
  • A gelatinous covering made of organic chemicals
  • Firmly attaches to the cell surface
  • Capsule help anchor S.mutans to anchor to
    surface of tooth

41
Capsule
  • Protects the cell from drying out
  • Prevents the bacteria from being recognized by
    the host
  • S. pneumoniae ? strain that lack capsule do not
    cause pneumonia

42
Pili Flagella
  • Presence or absence depends on species and
    conditions under which organism is grown
  • Spirochetes have a modified flagella?
    endoflagellum from the periplasmic space.

43
Pili
  • Straight hair like projections made of protein
    pilins
  • May be short or several cell lengths long

44
Pili
  • Main function is attachment? each type of
    bacteria attach to sp. surfaces
  • Present in virtually all Gm(-), absent in many
    Gm()

45
Sex Pili
  • Attaches one bacterial cell to another during
    mating

46
Flagella
  • Whip like structures that extend from the surface
    of the envelope
  • Function? Locomotion, allow bacteria to seek
    favorable conditions

47
Flagella Structure
  • Three distinct parts
  • Filament? flagellin protien arranged in chains
    forms a helix around a hollow core
  • Hook? short thickened bent region, act as a joint
  • Basal body? anchors filament hook to cell wall

48
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49
Flagella Arrangement
  • Monotrichous? single flagellum at one pole
  • Amphitrichous? single flagellum at each pole
  • Lopotrichous? two or more at one or both poles
  • Peritrichous? flagella all over the surface

50
Taxis
  • Chemotaxis ? bacteria sense certain chemicals and
    move toward nutrients or away from toxins
  • Phototaxis ? swim to optimum light
  • Magnetotaxis ?movement magnetic lines of force

51
Chemotaxis
52
Cytoplasm Inclusions
  • Cytoplasm ? grainy material that lies inside the
    CM
  • 90 water
  • Metabolism takes place here
  • Nucleoid? irregular mass of DNA in the cytoplasm,
    single circular molecule, carries genetic info.
  • Ribosomes ? protein making unit, 20,000/cell,
    smaller than eukaryotic ribosomes, 70S

53
Endospores
  • Resting structures
  • Most resistant biological structure known
  • Can withstand harsh environments
  • Can survive for 100s of years
  • Forms under unfavorable conditions, if conditions
    become favorable? germinate

54
Archeon
  • Do not have peptidoglycan
  • Cell Walls contain pseudomurein
  • Cytoplasmic membrane is also different

55
The Eukaryotic Animal Cell
56
The Eukaryotic Plant Cell
57
Eukarytotic Structures
  • External structures? cilia, flagella
  • Cell walls, Cell membranes
  • Cytoplasmic inclusions
  • Ribosomes
  • Cytoskeleton
  • Centrioles Centrosomes

58
Eukarytotic Structures
  • Nucleus contents
  • Endoplasmic Reticulum (rough smooth)
  • Golgi Body
  • Lysosomes
  • Mitochondria Chloroplasts

59
Nucleus contents
60
Endoplasmic Reticulum (rough smooth)
61
Ribosome
62
Protein Synthesis
63
Golgi Body
64
Lysosomes
65
Mitochondria
66
Chloroplasts
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