Download Rotavirus

Eukaryote
• Nucleus
• Paired
chromosomes
• Organelles
• Polysaccharide cell
walls
• Mitotic spindle
Prokaryote
No Nucleus
 One circular
chromosome
 No organelles
 Peptidoglycan cell
walls
 Binary fission

 Average
size: 0.2 -1.0 µm  2 - 8 µm
 Are unicellular and most multiply by
binary fission
 Basic shapes:
COCCUS
BACILLUS
SPIRAL
Arrangements
 Pairs:
Diplococci,
Diplobacilli
 Clusters:
Staphylococci
 Chains:
Streptococci,
Streptobacilli
Arrangements of cocci:
Determined by division of planes.
Arrangements of bacilli:
Determined by division of planes.
Arrangements of Spiral
bacteria
Double-stranded helix
formed by Bacillus
subtilis.
Bacterial structure
Prokaryote cell
Glycocalyx

Outside cell wall

Usually sticky

Capsule: Prevent
phagocytosis


A slime layer is
unorganized & loose
glycocalyx
Extracellular
polysaccharide
(EPS) allows cell to
attach
Figure 4.6a,
b
Flagella





Long filamentous
appendages
Outside cell wall
Made of chains of
flagellin
Attached to a
protein hook
Anchored to the wall
and membrane by
the basal body
Flagella Arrangement
Four arrangements of flagella:
Fimbriae and Pili


Short, thin appendages
Attachment
Cell Wall



Prevents osmotic lysis
Made of peptidoglycan
Contributes to disease capability and site of action of some
antibiotics.
Peptidoglycan


Polymer of disaccharide:
N-acetylglucosamine (NAG) & N-acetylmuramic acid
(NAM)
Linked by polypeptides
Small arrows: Where
penicillin interferes with
linkage of peptidoglycan
rows
Gram positive vs. gram negative cell walls
Gram-positive cell walls



Thick peptidoglycan
Teichoic acids
(alcohol+phosphate)
In acid-fast cells,
contains mycolic acid
(waxy lipid): Allows
them to be grouped
into medically
significant types.
Gram-negative cell walls
•
•
Thin peptidoglycan
•
Outer membrane:
No teichoic acids
o
o
Prevent phagocytosis
Barrier to certain
antibiotics
Gram-Positive cell walls



Teichoic acids:
– Lipoteichoic acid links to plasma membrane
– Wall teichoic acid links to peptidoglycan
May regulate movement of cations (+ charge)
Polysaccharides provide antigenic variation
(Identification)
Gram-Negative Outer Membrane






Lipopolysaccharides, lipoproteins, phospholipids.
Forms the periplasm between the outer membrane
and the plasma membrane.
Protection from phagocytes, antibiotics, and
complement (30+ liver proteins that protect host).
O polysaccharide antigen, e.g., E. coli O157:H7.
Lipid A is an endotoxin.
Porins (proteins) form channels through membrane
to pass other molecules
Gram-Negative Outer Membrane
Damage to Cell Walls

Lysozyme digests disaccharide in
peptidoglycan (Gram+ve cell walls: Destroyed,
Gram-ve cell wall: Damaged).

Penicillin inhibits peptide bridges in
peptidoglycan.
Plasma Membrane
Plasma Membrane: Fluid Mosaic
Model
Selectively permeable
 Phospholipid bilayer
 Peripheral proteins
 Integral proteins
 Transmembrane proteins

Figure 4.14b
Fluid Mosaic Model
Membrane is as viscous
as olive oil.
 Proteins: Movable
 Phospholipids: Movable

Plasma Membrane

Carry enzymes for metabolic reactions:
nutrient breakdown, energy production,
photosynthesis
Selective permeability allows passage of
some molecules
 Enzymes for ATP production
 Photosynthetic pigments on foldings called
thylakoids
 Damage to the membrane by detergents,
and polymyxin antibiotics causes leakage of
cell contents.
