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Chapter 4. Functional Anatomy of Prokaryotic and Eukaryotic Cells. Definition of “prokaryotic”. Refers to organisms, typically 1-celled, having cells which : lack a nucleus lack membrane-bound organelles contain 1 chromosome may contain extra-chromomal DNA (plasmids)

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chapter 4

Chapter 4

Functional Anatomy of

Prokaryotic and Eukaryotic

Cells

definition of prokaryotic
Definition of “prokaryotic”

Refers to organisms, typically 1-celled, having cells which:

  • lack a nucleus
  • lack membrane-bound organelles
  • contain 1 chromosome
  • may contain extra-chromomal DNA (plasmids)
  • contain 70S ribosomes
  • contain peptidoglycan cell walls
bacterial cell size shapes and arrangements
Bacterial cell size, shapes and arrangements
  • 2.0 – 10.0 uM in length
  • Eukaryotic cells ~10x larger
  • 3 common morphologies
    • bacillus = rod-shaped
    • coccus = spherical shaped
    • spirillum = spiral shaped
  • Many arrangements
    • diplo-
    • strepto-
    • Staphylo-

***spirochetes**

bacterial morphologies
Bacterial morphologies
  • Morphology can be used as an initial identifier
  • However, shape can change in some bacteria depending on environs
    • “pleomorphic” cells
1 cell wall structure
1) Cell wall structure
  • Alternating NAM & NAG amine sugars produce layers of block units
    • NAM = n-acetylmuramic acid
    • NAG = n-acetylglucosamine
  • Layers connected by tetrapeptide chains linked to NAM’s
  • Penta-glycine interbridges connect tetrapeptides in Gram + cells (sensitive to penicillin)
  • Direct peptide bonds connect tetrapeptides in Gram – cells (not sensitive to penicillin)

Make up peptidoglycan

gram positive cell wall structure
Gram positive cell wall structure

Ok, not too bad – now for something completely different – Gram negative cell walls!    

gram negative cell wall structure
Gram negative cell wall structure

Gram neg. cell walls are composed of peptidoglycan AND an outer membrane; it is multi-layered!!

gram negative lps
Gram negative LPS*
  • *Lipopolysaccharide contains 3 parts:
    • Antigen O – can change shape in dif’t environs
    • Core polysaccharide – contains neg. charge
    • Lipid A – also called ‘endotoxin A’; released upon cell death and can have toxic affect on nearby cell membranes
gram pos vs gram neg cell walls
Thick peptidoglycan

20-80 nm thick

Retains CV-I complex of Gram stain

Teichoic acid anchors cell wall to cell membrane and imparts a negative charge

Glycerol-P polymer

Two part structure

Thin peptidoglycan (10-20 nm)

Outer membrane

Outer membrane contains LPS

LPS imparts a negative charge

Gram pos. vs Gram neg cell walls

Gram +

Gram -

2 bacterial flagella
2) Bacterial flagella
  • Composed of: 1) basal body, 2) filament, 3) hook
  • Basal body connects to cell wall and to cell membrane
  • Uses ATP to spin
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