Flashcards in lecture 1.4 Deck (47):
What is peptidoglycan?
rigid, gigantic molecule that lies just outside the cell plasma membrane
What are the two types of cell walls?
Gram positive and Gram negative
Gram negative has what color?
Gram postive has what color?
How thick is a gram positive cell well?
How thick is a gram negative cell well?
What are the cell wall functions?
Maintains shape of the bacterium
Helps protect cell from osmotic lysis
Helps protect from toxic materials
May contribute to pathogenicity
What are gram positive cell walls made of?
Composed primarily of peptidoglycan
May also contain teichoic acids (negatively charged)
some gram-positive bacteria have layer of proteins on surface of peptidoglycan
What purpose do tetichoic acid serve?
help maintain cell envelope
protect from environmental substances
may bind to host cells
What is the periplamic space?
the space between the plasma membrane and cell wall
Describe the periplasmic space of Gram+ bacteria
is smaller than that of Gram-negative bacteria
Periplasm has relatively few proteins
Enzymes secreted by Gram-positive bacteria are called exoenzymes
aid in degradation of nutrients that are too large to be taken up
How is a gram- cell wall different than a gram+ cell wall?
More complex than Gram- positive
Consist of a thin layer of peptidoglycan surrounded by an outer membrane
Outer membrane composed of lipids, lipoproteins, and lipopolysaccharide (LPS)
No teichoic acids
How much weight does the peptidoglycan make of a cell wall?
~5-10% of cell wall weight
How does the periplasmic space of gram- differ from gram+ cells
may constitute 20–40% of cell volume
many enzymes present in periplasm
hydrolytic enzymes, transport proteins and other proteins
What does the outer membrane in gram- cells encompass?
Surrounds the peptifdoglycan and periplasmic space?
How much weight does the peptidoglycan make up of gram negative cell walls?
How much cell volume of gram negative cell walls does the Periplasmic space take up?
What is in the periplasmic space?
Enzymes, hydrolytic enzymes, transport proteins and other proteins
What is the outer membrane called?
Where is the lipopolysaccharide?
outside the thin peptidoglcan layer
What connects the outer membrane to peptidoglycan?
What are Braun's lipoproteins?
connect outer membrane to peptidoglycan
What are the three parts of a lipoplysaccharide?
Lipid A, core polysaccharide, and O side
What is O side chain?
What part of the lipopolysaccharide (LPS) extends out from the cell?
O side chain
What is special/characterizes the outer membrane in gram negative cells?
second a permeability barrier (adding cyto memb)
protection from host defenses (O antigen)
can act as an endotoxin (lipid A)
contributes to negative charge on cell surface
helps stabilize outer membrane structure
may contribute to attachment to surfaces and biofilm formation
Is the outer membrane of gram negative more or less permeable than the plasma membrane and why?
More permeable than plasma membrane due to presence of porin proteins and transporter proteins
Why does gram staining differentiate between gram positive and gram negative?
It happens by shrinkage of pores in peptidoglycan layer
gram positive has a large peptidoglycan layer so it becomes impermeable
gram negative have a small peptidoglycan layer so it is still permeable
Describe a hypotonic solution and how the cell deals with it
solute concentration outside cell less than inside
water moves into cell and cell swells
cell wall protects from lysis
Describe a hypertonic solution and how the cell deals with it
solute concentration outside cell greater than inside
water leaves the cell
What does lysozyme do?
breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid
What breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid?
What does penicillin do?
inhibits peptidoglycan synthesis
What inhibits peptidoglycan synthesis?
What happens if a cell is treated with penicillin or peptidoglycan?
they will lyse if they are in a hypotonic solution
What are protoplasts/spheroplasts?
derivatives of bacteria formed by removal or weakening of the cell wall, leaving intact cytoplasmic membrane that contains the cytoplasm.
what are derivatives of bacteria formed by removal or weakening of the cell wall, leaving intact cytoplasmic membrane that contains the cytoplasm?
What are some bacteria that lack peptidoglycan?
Chlamydia, Planctomycetes, Myoplasma
What characterizes a capsule?
composed of polysaccharides
well organized, hard to remove
visible in light microscope
What are the protective advantages of a capsule?
resistant to phagocytosis
protect from desiccation
exclude viruses and detergents
What characterizes a slime layer?
similar to capsule
may aid in motility
How do capsules and slime layers differ?
slime layers diffuse, unorganized and are easily removed while capsules are not
What is an S layer?
Regularly structured layers of protein or glycoprotein that self-assemble
What does the S layer adhere to in gram negative cellsl?
What is the S layer associated with in gram positive cells?