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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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