Wednesday Notes


Bacteria: External Structures

Flagella: Long; used for motility

Fimbriae: Used to attache to other cells & inanimate objects

Pili (penis-ish) – Exchanges DNA


Flagellum (latin for whip)

3 Parts

  1. Filament – Composed of a protein called flagellin
  2. Hook – Base of filament near cell wall
  3. Basal Body – Anchors filament & hook to cell wall

Rotates: 360° turns clockwise (tumbles) & counterclockwise (runs)


  • Petritrichous – flagella cover entire surface
  • Polar – Flagella @ one or both ends. Possible more than one.
  • Axial Filaments (AKA Endofilaments)- flagella at both ends that spiral around cell between cytoplasmic membrane & outer membrane

Taxis (Movement): Bacterial motility in response to environmental stimuli

Positive: Movement toward stimulus 

Negative: Movement away from stimulus


  • Light – Phototaxis
  • Chemicals – chemotaxis

Bacterial Cells: Fimbriae & Pili the “penis”


  • Fimbriae – Attache to other cells & inanimate objects
  • Pili –  Exchanges genetic information. Composed of pilin (protein)

F + … male cell

F – …female cell

Bacterial Cell Walls:

Walls made of peptidoglycan…


  • Complex polysaccharides
  • Alternating monosaccharide molecules in chains bonded together by polypeptides
  • N – Acetylglucosamine (NAG) & N – Acetylmuramic Acid (NAM) these alternate

Tertapeptide holds vertical layers & amino acids connects horizontal layers. (look this up, this a poor explanation)

Gram Positive Cell Walls vs. Gram Negative Cell Walls

Gram-Positive cell walls:

  1. Cytoplasmic membrane
  2. multiple layers of peptidoglycan
  3. teichoic acid (contained in the peptidoglycan)
  4. acid gives cell wall negative charge

Gram-Negative Cell Walls:

  1. Cytoplasmic membrane
  2. Few layers of peptidoglycan
  3. Outer membrane (phospholipids) – Contains lipo polysaccharieds & a substance called Lipid A which triggers immune system because it is toxic to mammalian cells

Bacteria Cells: Cystoplasmic Membranes


  • Bilayer of phospholipids
  • Proteins: Integral (around); peripheral (inside)


  • Semi-permeable membrane (some molecule can pass through, not all)
  • Protective
  • Fluid/semi-fluid

No lab notes today.


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