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Microbio 3220 > Exam 1 - Lecture 3 > Flashcards

Exam 1 - Lecture 3 Flashcards

1
Q

what are the three types of peptidoglycan variations?

A
  • composition of linkage (direct or bridges)
  • amino acid at #3 position
  • linkage type (2 to 4, 3 to 4)
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2
Q

which type of amino acid is usually only found in bacterial cell walls, L- or D-?

A

D- amino acids

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3
Q

what kind of linkage connects NAM and NAG sugars?

A

beta-(1,4) glycosidic bonds

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4
Q

how thick is the peptidoglycan layer in Gram-positive cell walls?

A

20-80 nm thick

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5
Q

what are teichoic acids?

are they found in Gram-positive or Gram negative cell walls?

A
  • negatively charged acids that help maintain the cell envelope, protect from environmental substances, and may bind to host cells
  • only found in Gram-positive walls
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6
Q

what are teichoic acids composed of?

A

alternating phosphate and glycerol groups

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7
Q

where can you find teichoic acids? what about lipoteichoic acids?

A

teichoic: covalently attached to peptidoglycan

lipoteichoic: covalently attached to lipids in plasma membrane

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8
Q

what is the cell wall protein sequence in Gram-positive cell walls?

which residue of the sequence is covalently linked to peptidoglycan via what enzyme?

A
  • LPXTG
  • T residue, Sortase
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9
Q

what is an LPS?

A

lipopolysaccharide

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10
Q

how many membranes does a Gram-negative cell wall have?

what are they called?

A
  • two
  • outer membrane and inner/plasma membrane
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11
Q

do Gram-negative cells have teichoic acids?

A

nope

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12
Q

what connects the outer membrane to the peptidoglycan in Gram-negative bacteria?

A

Braun’s lipoprotein

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13
Q

what is the inner leaflet of the outer membrane composed of in Gram-negative bacteria?

A

phospholipids

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14
Q

what is the outer leaflet of the outer membrane composed of in Gram-negative bacteria?

A

lipopolysaccharide (LPS)

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15
Q

where is LPS found?

A

only in Gram-negative bacteria

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16
Q

what are the three parts of LPS?

A
  • O antigen
  • core polysaccharide
  • Lipid A
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17
Q

what parts of LPS are embedded in the outer membrane, and which extend out from the cell?

A

Lipid A is embedded in the outer membrane

O antigens and the core polysaccharide extend from the cell

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18
Q

what is the importance of LPS?

A
  • contributes to negative charge on cell surface (core polysaccharide)
  • stabilizes the outer membrane (Lipid A)
  • protects from host defenses (O antigen)
  • creates permeability barrier
  • can act as a toxin (lipid A)
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19
Q

how many endotoxins do we have?

A

one! (LPS’s Lipid A)

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20
Q

what makes the outer membrane permeable?

A

the presence of porin proteins: channels that let small molecules pass through

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21
Q

what is the mechanism of Gram-staining in Gram-positive cells?

A

the constriction/shrinkage of the thick peptidoglycan layer prevents loss of crystal violet during decolorization

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22
Q

why doesn’t the peptidoglycan layer in Gram-negative cells retain crystal violet?

A

the peptidoglycan layer is thinner and more porous

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23
Q

can you explain the steps of Gram-staining?

A
  • crystal violet dye is added
  • iodine is added
  • complex forms between CV and iodine
  • the sample is decolorized (with ethanol)
  • the thinner Gram-negative cells lose their color, Gram-positive stays purple
  • a counterstain, safranin, is added
  • Gram-positive cells are now pink
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24
Q

what protects bacterial cells from osmotic stress?

A

the cell wall

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25
Q

what is a hypotonic environment?

A
  • the solute concentration is higher inside the cell
  • water moves into the cell and cell swells
  • cell wall protects from lysis
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26
Q

what is a hypertonic environment?

A
  • the solute concentration is higher outside the cell
  • water leaves the cell
  • plasmolysis occurs (shrinking of the cytoplasm)
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27
Q

what do we call Gram-positive bacteria without the peptidoglycan?

A

protoplasts

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28
Q

what do we call Gram-negative bacteria without the peptidoglycan?

A

spheroplasts

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29
Q

if the peptidoglycan cell wall is removed, the cells will lyse in _____tonic solution and survive in _____tonic solution

A

hypotonic; isotonic

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30
Q

what are the three most common types of external layers found in bacteria?

A
  • capsules
  • slime layers
  • S-layers
31
Q

what is the role of the external layer in bacteria?

A

plays a role in interaction of the bacterial cell and its environment

32
Q

what are capsules composed of?

A

polysaccharides (sugars)

33
Q

true of false: capsules are well organized and not easily removed from the cell.

A

true

34
Q

what are the protective advantages of capsules?

A
  • resistant to phagocytosis
  • protect from desiccation
  • exclude viruses and detergents
35
Q

true of false: slime layers are well organized and not easily removed from the cell.

A

false; slime layers diffuse, are unorganized, and are removed easily

36
Q

what might slime layers aid in?

A

motility

37
Q

what are S-layers?

A

regularly structured layers of protein or glycoproteins that self-assemble

38
Q

where does the S-layer adhere to in Gram-negative bacteria?

Gram-positive bacteria?

A
  • the outer membrane
  • the peptidoglycan surface
39
Q

what is the cytoplasm?

A

material bound by the plasmid membrane

40
Q

what are the five bacterial cytoplasmic structures?

A
  • cytoskeleton
  • intracytoplasmic structures
  • ribosomes
  • nucleiod and plasmids
  • inclusions
41
Q

what are the three eukaryotic cytoskeletal elements?

A
  • actin
  • tubulin
  • intermediate filaments

(homologues of all three have been found in bacteria)

42
Q

what is FstZ? where is it found?

A
  • a tubulin homologue that aids in septum formation during cell division
  • found in many bacteria
43
Q

what is MreB? where is it found?

A
  • an actin homologue that maintains shapes by positioning peptidoglycan synthesis machinery
  • found in rods
44
Q

what is CreS and where is it found?

A

a rare intermediate filament homologue that maintains the shape of curve shaped bacteria

45
Q

what does the S in 16S, 80S, etc., stand for?

A

Svedberg unit

46
Q

what are ribosomes?

A

sites for protein synthesis

47
Q

how big is the eukaryotic ribosome?

prokaryotic (archaeal and bacterial)?

A
  • 80S
  • 70S
48
Q

what ribosomal RNA is found in bacteria (large and small subunits)?

A
  • small subunit: 16S
  • large subunit: 23S and 5S
49
Q

what is in the nucleoid of a cell?

A

the genetic material

50
Q

what are plasmids?

A

extrachromosomal DNA (like extra DNA)

51
Q

what does it mean when a cell is “cured”?

A

it has “lost” its plasmids

52
Q

true or false: plasmids exist and replicate independently of the chromosome and can be inherited during cell division?

A

true

53
Q

true of false: there can only be one copy of plasmid in a cell

A

false; there can be multiple

54
Q

plasmid genes are (essential or non-essential)?

A

non-essential

55
Q

what are inclusions? what is another name for them?

A
  • granules of organic or inorganic material stockpiled by the cell for future use
  • sometimes called microcompartments
56
Q

what are the three best known examples of external structures in bacteria?

A

pili, fimbriae, and flagella

57
Q

what are the four functions of external structures in bacteria?

A
  • attachment to surfaces
  • cell movement
  • protection
  • horizontal gene transfer
58
Q

what is conjugation in bacteria?

A

transfer of plasmid from one cell to another

59
Q

what is the main function of flagella?

A

motility

60
Q

what does it mean when a bacteria is monotrichous?

A

it has one flagella

61
Q

what does it mean when a bacteria is amphitrichous?

A

it has one flagella at each end

62
Q

what does it mean when a bacteria is lophotrichous?

A

it has a cluster of flagella at one or both ends

63
Q

what does it mean when a bacteria is peritrichous?

A

it has flagella spread over the entire surface of the cell

64
Q

what are the three parts of flagella?

A
  • filament
  • hook
  • basal body
65
Q

filament subunits self-assemble with the help of filament caps at the (tip or base).

A

tip, NOT base

66
Q

what is chemotaxis?

A

moving towards chemical attractants such as nutrients, and away from harmful substances

67
Q

what are the four common types of motility?

A
  • flagellar movement
  • spirochete motility
  • twitching motility
  • gliding motility
68
Q

match the following flagellar movements:

a.) clockwise
b.) counterclockwise

1.) run (forward motion)
2.) tumble (turning)

A

b1.) counterclockwise is run

a2.) clockwise is tumbling

69
Q

in spirochetes, where do the flagella remain?

A

the periplasmic space inside the outer membrane

70
Q

which describes short, intermittent, jerky motions:

gliding or twitching?

A

twitching

71
Q

in the presence of a chemical attractant, does CW rotation of flagella increase or decrease? why?

A

CW (tumbling) decreases so that the run (CCW) in the direction of the attractant is longer

72
Q

when concentration of a chemical attractant decreases, does CW rotation of flagella increase or decrease? why?

A

CW (tumbling) increases so that the cell can redirect until it is moving toward the attractant again

73
Q

what is sporulation? what is its purpose?

A
  • endospore formation by bacteria
  • survival and preservation of the genetic material (NOT reproduction)
74
Q

what are the three steps of formation of vegetative cells?

A
  • activation (of spores)
  • germination
  • outgrowth

Microbio 3220 (24 decks)

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