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Microbiology > The Cell Wall > Flashcards

The Cell Wall Flashcards

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Biology 101 flashcards
1
Q

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

A

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

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2
Q

what are three antibiotics that utilize cell wall active sites?

A

penicillin, cephalosporins, vancomycin

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3
Q

What is the cell wall in bacteria composed of?

A

peptidoglycan (murein)

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4
Q

What is the basic structure of the bacterial cell wall?

A

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

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5
Q

what are the two sugars in the glycan chain?

A

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

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6
Q

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

A

Beta 1,4 - glycosidic linkages

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7
Q

What is the phylum of gram + bacteria?

A

Firmicutes

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8
Q

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

A

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

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9
Q

What is the phylum of gram - bacteria?

A

Proteobacteria

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10
Q

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

A

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

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11
Q

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

A

they make it more difficult to break down by proteases

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12
Q

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

A

A crosslink bridge composed of 5 amino acids?

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13
Q

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

A

a direct crosslink with no amino acids

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14
Q

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

A

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

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15
Q

Why is a cell wall necessary in prokaryotes?

A

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.

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16
Q

What antibiotics have an active site in the cell wall?

A

penicillin, cephalosporins, vancomycins

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17
Q

what is murein?

A

peptidoglycan

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18
Q

What is the glycan chain composed of in bacteria?

A

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

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19
Q

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

A

T

20
Q

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

A

lysozyme

21
Q

What are 3 features of Gram + bacteria?

A

no outer membrane
thick cell wall
contains teichoic acids

22
Q

What are 2 features of Gram - bacteria

A

outer membrane
thin cell wall

23
Q

What is teichoic acid?

A

chains of phosphodiester linked glycerol or ribitol

24
Q

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

A

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

25
Q

What is a lipoteichoic acid?

A

a teichoic acid that is embedded in the cell membrane

26
Q

What is lipopolysaccharide?

A

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

27
Q

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

A

Brauns lipoprotein, connects to cell wall

28
Q

What are the 4 steps of gram staining?

A
  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
29
Q

What stain is used to identify mycobacterium?

A

acid-fast stain

30
Q

What is arabinogalactan?

A

a long polysaccharide made up of arabinose and galactose

31
Q

T/F, mycobacterium have no peptidoglycan

A

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

32
Q

What are the two components of the mycomembrane?

A

inner leaflet and outer leaflet

33
Q

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

A

mycolic acid

34
Q

what is mycolic acid?

A

a long hydrocarbon with 2 tails.

35
Q

How long are the two hydrocarbon tails in mycolic acid

A

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

36
Q

Why do mycobacterium grow slowly?

A

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

37
Q

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

A

true

38
Q

Give 3 structural features of mycoplasma

A

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

39
Q

What is the cell wall in archaea made up of?

A

pseudopeptidoglycan

40
Q

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

A

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

41
Q

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

A

varying amino acids used, all in the L conformation

42
Q

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

A

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

43
Q

What are S layers?

A

consist of interlocking proteins or glycoproteins that form a paracrystalline structure

44
Q

what are 3 features of S layers?

A

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

45
Q
A

Microbiology (30 decks)

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