lecture 1.4

Question 1

What is peptidoglycan?

Answer 1

rigid, gigantic molecule that lies just outside the cell plasma membrane

Question 2

What are the two types of cell walls?

Answer 2

Gram positive and Gram negative

Question 3

Gram negative has what color?

Answer 3

pink

Question 4

Gram postive has what color?

Answer 4

purple

Question 5

How thick is a gram positive cell well?

Answer 5

20-80 nm

Question 6

How thick is a gram negative cell well?

Answer 6

2 nm

Question 7

What are the cell wall functions?

Answer 7

Maintains shape of the bacterium
Helps protect cell from osmotic lysis
Helps protect from toxic materials
May contribute to pathogenicity

Question 8

What are gram positive cell walls made of?

Answer 8

Composed primarily of peptidoglycan
May also contain teichoic acids (negatively charged)
some gram-positive bacteria have layer of proteins on surface of peptidoglycan

Question 9

What purpose do tetichoic acid serve?

Answer 9

help maintain cell envelope
protect from environmental substances
may bind to host cells

Question 10

What is the periplamic space?

Answer 10

the space between the plasma membrane and cell wall

Question 11

Describe the periplasmic space of Gram+ bacteria

Answer 11

is smaller than that of Gram-negative bacteria
Periplasm has relatively few proteins
Enzymes secreted by Gram-positive bacteria are called exoenzymes

Question 12

exoenymes=

Answer 12

aid in degradation of nutrients that are too large to be taken up

Question 13

How is a gram- cell wall different than a gram+ cell wall?

Answer 13

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

Question 14

How much weight does the peptidoglycan make of a cell wall?

Answer 14

~5-10% of cell wall weight

Question 15

How does the periplasmic space of gram- differ from gram+ cells

Answer 15

may constitute 20–40% of cell volume
many enzymes present in periplasm
hydrolytic enzymes, transport proteins and other proteins

Question 16

What does the outer membrane in gram- cells encompass?

Answer 16

Surrounds the peptifdoglycan and periplasmic space?

Question 17

How much weight does the peptidoglycan make up of gram negative cell walls?

Answer 17

5-10%

Question 18

How much cell volume of gram negative cell walls does the Periplasmic space take up?

Answer 18

20-40%

Question 19

What is in the periplasmic space?

Answer 19

Enzymes, hydrolytic enzymes, transport proteins and other proteins

Question 20

What is the outer membrane called?

Answer 20

Lipopolysaccharide (LPS)

Question 21

Where is the lipopolysaccharide?

Answer 21

outside the thin peptidoglcan layer

Question 22

What connects the outer membrane to peptidoglycan?

Answer 22

Braun’s lipoprotiens

Question 23

What are Braun’s lipoproteins?

Answer 23

connect outer membrane to peptidoglycan

Question 24

What are the three parts of a lipoplysaccharide?

Answer 24

Lipid A, core polysaccharide, and O side

Question 25

What is O side chain?

Answer 25

O antigen

Question 26

What part of the lipopolysaccharide (LPS) extends out from the cell?

Answer 26

O side chain

Question 27

What is special/characterizes the outer membrane in gram negative cells?

Answer 27

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

Question 28

Is the outer membrane of gram negative more or less permeable than the plasma membrane and why?

Answer 28

More permeable than plasma membrane due to presence of porin proteins and transporter proteins

Question 29

Why does gram staining differentiate between gram positive and gram negative?

Answer 29

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

Question 30

Describe a hypotonic solution and how the cell deals with it

Answer 30

solute concentration outside cell less than inside water moves into cell and cell swells cell wall protects from lysis

Question 31

Describe a hypertonic solution and how the cell deals with it

Answer 31

solute concentration outside cell greater than inside water leaves the cell plasmolysis occurs

Question 32

What does lysozyme do?

Answer 32

breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid

Question 33

What breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid?

Answer 33

Lysozyme

Question 34

What does penicillin do?

Answer 34

inhibits peptidoglycan synthesis

Question 35

What inhibits peptidoglycan synthesis?

Answer 35

penicillin

Question 36

What happens if a cell is treated with penicillin or peptidoglycan?

Answer 36

they will lyse if they are in a hypotonic solution

Question 37

What are protoplasts/spheroplasts?

Answer 37

derivatives of bacteria formed by removal or weakening of the cell wall, leaving intact cytoplasmic membrane that contains the cytoplasm.

Question 38

what are derivatives of bacteria formed by removal or weakening of the cell wall, leaving intact cytoplasmic membrane that contains the cytoplasm?

Answer 38

Protoplasts/spheroplasts

Question 39

What are some bacteria that lack peptidoglycan?

Answer 39

Chlamydia, Planctomycetes, Myoplasma

Question 40

What characterizes a capsule?

Answer 40

composed of polysaccharides well organized, hard to remove visible in light microscope protective advantage

Question 41

What are the protective advantages of a capsule?

Answer 41

resistant to phagocytosis protect from desiccation exclude viruses and detergents

Question 42

What characterizes a slime layer?

Answer 42

similar to capsule unorganized easily removed may aid in motility

Question 43

How do capsules and slime layers differ?

Answer 43

slime layers diffuse, unorganized and are easily removed while capsules are not

Question 44

What is an S layer?

Answer 44

Regularly structured layers of protein or glycoprotein that self-assemble

Question 45

What does the S layer adhere to in gram negative cellsl?

Answer 45

outer membrane

Question 46

What is the S layer associated with in gram positive cells?

Answer 46

Peptidogylcan surface

Question 47

What are the functions of an S layer?

Answer 47

``` Protect from ion and pH fluctuations, osmotic stress, enzymes, and predation Maintains shape and rigidity Promotes adhesion to surfaces Protects from host defenses Potential use in nanotechnology S layer spontaneously associates ```