Download Bacteria and their cell walls

Bacterial Cell Envelope
The Pilus
Bacterial Cell Envelope
• The cell envelope is made up of:
– Capsule
– Cell wall
– Cell membrane
• The cell envelope provides the bacteria
with:
– Structure
– Transportation of materials in/out
The Capsule
The Capsule



Made of polysaccharides
and protein
Protects against
dehydration, harmful
chemicals, &
phagocytosis
Attaches bacteria to
surfaces
Cell Walls
• 2 main types of bacterial cell walls:
– Gram positive
– Gram negative
• Named after Christian Gram, a physician
who discovered the technique used to
differentiate bacteria
Cell Walls
Gram Positive Cell Wall
Gram Positive Cell Wall
Gram Staining
• Bacteria that are
“Gram positive”
appear violet when
stained
Gram Negative Cell Wall
Gram Negative Cell Wall
Gram Staining
• Bacteria that are
“Gram negative”
appear red
Lipopolysaccharides
• Only found in Gram negative bacteria cell
walls
• Provides structure and protection
• Considered to be toxic to animals and
results in:
– Fever
– Inflammation
– Potentially fatal
Positive & Negative Comparison
Warm-Up
• What are the differences between Gram
positive and Gram negative cells?
Cell Membrane
Phospholipid
Phospholipid Bilayer
Phospholipid Bilayer
Cell Membrane
Cell Membrane Transport
• Membrane is selectively permeable
– Material that normally dissolves in lipids can
pass through the membrane
– Large particles and charged particles often
cannot pass through the membrane
– Certain substances (like amino acids) have to
pass through special protein passageways