The Cell Wall

Question 1

What are the five main functions/uses of the bacterial cell wall

Answer 1

protect against osmotic pressure (lysis)
determine cell shape
protect against toxic substances
contribute to pathogenicity
contain the active site for several antibiotics

Question 2

what are three antibiotics that utilize cell wall active sites?

Answer 2

penicillin, cephalosporins, vancomycin

Question 3

What is the cell wall in bacteria composed of?

Answer 3

peptidoglycan (murein)

Question 4

What is the basic structure of the bacterial cell wall?

Answer 4

peptid crosslinks (4 amino acids) sandwiched in between two glycan chains

Question 5

what are the two sugars in the glycan chain?

Answer 5

N-acetylglucosamine (NAG), and N-acetylmuramic acid (NAM)

Question 6

What kind of linkage is between the two sugars in the glycan chain?

Answer 6

Beta 1,4 - glycosidic linkages

Question 7

What is the phylum of gram + bacteria?

Answer 7

Firmicutes

Question 8

What is the structure of the gram + bacterial cell wall?

Answer 8

NAM , L-alanine , D-hydroxylated glutamic acid , L-lysine , D - alanine

Question 9

What is the phylum of gram - bacteria?

Answer 9

Proteobacteria

Question 10

what is the structure of a gram - bacterial cell wall?

Answer 10

NAM, L-alanine, D-glutamic acid, diaminopimolic acid (DAP), D-alanine

Question 11

Why are L and D linkages important in the bacterial cell wall?

Answer 11

they make it more difficult to break down by proteases

Question 12

In Gram + bacteria, what links the L-lysine and D-alanine?

Answer 12

A crosslink bridge composed of 5 amino acids?

Question 13

In Gram - bacteria, what links the diaminopimelic acid and D-alanine?

Answer 13

a direct crosslink with no amino acids

Question 14

What are the major differences between Gram + and Gram - bacteria?

Answer 14

Gram + bacteria have no outer membrane, a large thick cell wall with 4-25 sheets, and contain teichoic acids.
Gram - bacteria have an outer membrane, and a thin cell wall with 1-3 sheets

Question 15

Why is a cell wall necessary in prokaryotes?

Answer 15

due to the lack of membrane bound organelles, there is a large amount of dissolved solute right in the cytoplasm, this leads to a high osmotic pressure with the tendency of water to come into the cell. the cell wall prevents this.

Question 16

What antibiotics have an active site in the cell wall?

Answer 16

penicillin, cephalosporins, vancomycins

Question 17

what is murein?

Answer 17

peptidoglycan

Question 18

What is the glycan chain composed of in bacteria?

Answer 18

N-acetylglucosamine, N-acetylmuramic acid. Linked by a B 1,4, glycosidic linkage

Question 19

T/F, peptides will always come off of N-acetylmuramic acid

Answer 19

T

Question 20

What part of our innate immune system can break up the B 1,4 linkages in the peptide chains?

Answer 20

lysozyme

Question 21

What are 3 features of Gram + bacteria?

Answer 21

no outer membrane
thick cell wall
contains teichoic acids

Question 22

What are 2 features of Gram - bacteria

Answer 22

outer membrane
thin cell wall

Question 23

What is teichoic acid?

Answer 23

chains of phosphodiester linked glycerol or ribitol

Question 24

How do glycerol and ribitol allow for modification of teichoic acids?

Answer 24

can find D-alanine or glucose attached to the glycerol or ribitol

Question 25

What is a lipoteichoic acid?

Answer 25

a teichoic acid that is embedded in the cell membrane

Question 26

What is lipopolysaccharide?

Answer 26

a 3 component molecule that takes up most of the outer leaflet of the outer membrane

Question 27

What is the inner leaflet of the outer membrane composed of?

Answer 27

Brauns lipoprotein, connects to cell wall

Question 28

What are the 4 steps of gram staining?

Answer 28

1. crystal violet (primary stain) both cell walls affix the dye 2. grams iodine (fixative) both cell walls still purple 3. Alcohol (decolorizer) Gram - now colorless 4. Safranin (red dye) stains Gram - pink

Question 29

What stain is used to identify mycobacterium?

Answer 29

acid-fast stain

Question 30

What is arabinogalactan?

Answer 30

a long polysaccharide made up of arabinose and galactose

Question 31

T/F, mycobacterium have no peptidoglycan

Answer 31

F, have a very thin layer with a higher degree of crosslinking

Question 32

What are the two components of the mycomembrane?

Answer 32

inner leaflet and outer leaflet

Question 33

What is the inner leaflet of the outer membrane composed of in mycobacterium?

Answer 33

mycolic acid

Question 34

what is mycolic acid?

Answer 34

a long hydrocarbon with 2 tails.

Question 35

How long are the two hydrocarbon tails in mycolic acid

Answer 35

one is 20 Carbons long, the other is 60-90 carbons long

Question 36

Why do mycobacterium grow slowly?

Answer 36

the combination to the dense sugar network and the hydrophobic mycomembrane covering the peptidoglycan makes getting nutrients in difficult

Question 37

T/F mycoplasma is the most common contaminant of tissue culture cells

Answer 37

true

Question 38

Give 3 structural features of mycoplasma

Answer 38

no cell wall sterols found in membrane for structural integrity extremely tiny 0.1-0.5 micrometers

Question 39

What is the cell wall in archaea made up of?

Answer 39

pseudopeptidoglycan

Question 40

What two sugars make up pseudopeptidoglycan in archaea and what links them

Answer 40

N-acetylglucosamine and N-acetyltalosaminuronic acid, linked by a B 1,3 glycosidic linkage

Question 41

what are the peptide crosslinks made up of in archael cell walls?

Answer 41

varying amino acids used, all in the L conformation

Question 42

How come archaea have all L sugars, even though proteases can then break them down

Answer 42

archaea are extremophiles, they primarily don't interact with hosts and therefore do not need to be immune to proteases

Question 43

What are S layers?

Answer 43

consist of interlocking proteins or glycoproteins that form a paracrystalline structure

Question 44

what are 3 features of S layers?

Answer 44

form a sheath around the cell common to see in archaea, paracrystalline structure with symmetry that can be hexagonal, tetragonal, trimeric