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Vet Microbio > Bacterial Cell Structure > Flashcards

Bacterial Cell Structure Flashcards

1
Q

what is arrangement determined by?

A

the plane of division and by separation/lack of separation

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2
Q

what are the seven shapes of bacteria?

A
  1. coccus
  2. coccobacillus
  3. bacillus
  4. vibrio
  5. spirillum
  6. spirochete
  7. pleomorphic
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3
Q

cocci characteristics

A

diplococci- pairs
streptococci- chains
staphylococci- grape-like clusters
tetrads- 4 cocci in a square
sarcinae- cubic configuration of 8 cocci

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4
Q

bacilli characteristics

A

rods
coccobacilli- very short rods

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5
Q

vibrios

A

resemble rods, comma shaped

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6
Q

spirilla

A

rigid helices

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7
Q

spirochetes

A

flexible helices

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8
Q

mycelium

A

network of long, multinucleate filaments

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9
Q

pleomorphic

A

organisms that are variable in shape

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10
Q

what is the smallest type of bacteria?

A

mycoplasma

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11
Q

what is the largest bacteria?

A

Epulopiscium fishelsoni

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12
Q

Protoplast

A

the plasma membrane and everything within

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13
Q

cytoplasm

A

material bounded by the plasma membrane

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14
Q

cytosol

A

liquid portion of cytoplasm; does not include genetic material, ribosomes, etc.

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15
Q

inclusions

A

granules of organic or inorganic material that are stockpiled by the cell for future use
some are enclosed by a single-layered membrane

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16
Q

ribosomes

A

complex protein/RNA structures
-sites of protein synthesis
-bacterial and archaea ribosomes are 70S
-eukaryotes are 80S

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17
Q

what does 16S mean?

A

working with microbes

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18
Q

nucleoid

A

usually not membrane bound
location of chromosome and associated proteins
usually 1 closed circular, double stranded molecule
supercoiling and nuclei proteins aid in folding

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19
Q

plasmids

A

extrachromosomal DNA that is found in bacteria, archaea, and some fungi
usually small, closed circular DNA molecules

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20
Q

how do plasmids exist and replicate?

A

independently of chromosome
inherited during cell division

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21
Q

what is the function of plasmids?

A

to confer selective advantages to host

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22
Q

what are some of the benefits of plasmids?

A

antibiotic resistance, extreme temp adjustment, utilization of nutrients, reproduce quicker, increase metabolism

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23
Q

what are the functions of the plasma membrane?

A

encompasses the cytoplasm
selectively permeable barrier
interacts with external environment

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24
Q

how does the plasma membrane interact with the external environment?

A

receptors for detection of and response to chemicals in surroundings
transport systems
metabolic processes

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25
Q

what are amphipathic lipids?

A

polar ends and non-polar tails that make up the lipid bilayers

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26
Q

peripheral membrane proteins characteristics

A

loosely connected to membrane and easily removed

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27
Q

integral membrane protein characteristics

A

amphipathic- embedded within membrane
carry out important functions

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28
Q

peptidoglycan

A

rigid structure that lies just outside the cell plasma membrane
mesh-like polymer of two alternating sugars forming long strands

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29
Q

what are the two alternating sugars that form the long strands of peptidoglycan?

A

NAG and NAM

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30
Q

what are the two types of cell wall?

A

gram-positive and gram-negative

31
Q

what are the characteristics of gram-positive cell walls?

A

stain purple; thick peptidoglycan

32
Q

what are the characteristics of gram-negative cell walls?

A

stain pink or red; thin peptidoglycan and outer membrane

33
Q

functions of the cell wall

A

maintains the shape of the bacterium
helps protect cell from osmotic lysis
helps protect from toxic materials
may contribute to pathogenicity

34
Q

gram positive cell walls

A

composed primarily of peptidoglycan
may contain teichoic acids, making it negatively charged
can have layers of proteins on surface of peptidoglycan

35
Q

what do teichoic acids do to gram-positive cell walls?

A

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

36
Q

periplasmic space in gram positive bacteria

A

lies between plasma and cell wall and is smaller than that of gram-negative
has relatively few proteins

37
Q

gram-negative cell wall characteristics

A

more complex than gram positive
consist of a thin layer of peptidoglycan surrounded by an outer membrane
outer membrane composed of lipids, lipoproteins, and lipopolysaccharides in stead of teichoic acids

38
Q

how does the periplasmic space of gram-negative cells differ from that of gram-positive cells?

A

may constitute 20-40% of cell volume
there are many enzymes present- hydrolytic enzymes, transport proteins, and other proteins

39
Q

what connects the outer membrane to peptidoglycan in gram-negative cell walls?

A

Braun’s lipoproteins

40
Q

what are the three parts of lipopolysaccharides?

A
  1. lipid A embedded in outer membrane
  2. core polysaccharide
  3. O side chains (antigen) that extend out from the cell
41
Q

what is the importance of LPS?

A

contributes to the negative charge on cell surface
helps stabilize outer membrane structure
may contribute to attachment to surfaces and biofilm formation
creates a permeability barrier
protection from host defenses (O antigen)
can act as an endotoxin (lipid A)

42
Q

what causes people to get sick from Ecoli 0157?

A

the O antigen

43
Q

what makes up the glycocalyx?

A

capsule and slime layers

44
Q

what is the function of the capsule layer?

A

aids in attachment to solid surfaces such as biofilms in plants and animals

45
Q

capsule layer characteristics

A

usually composed of polysaccharides
well organized and not easily removed from the cell
visible in light microscope
provides protective advantages

46
Q

what are the protective advantages of the capsule layer?

A

resistant to phagocytosis
protect from desiccation
exclude viruses and detergents

47
Q

what are the slime layers?

A

similar to capsules except diffuse, unorganized, and easily removed
may aid in motility

48
Q

what are the S layers?

A

regularly structured layers of protein or glycoprotein that self-assemble

49
Q

how does the S-layer differ between Gram-negative and Gram-positive bacteria?

A

gram-negative: the S layer adheres to the outer membrane
gram-positive: it is associated with the peptidoglycan surface

50
Q

what are the functions of the S layer?

A

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

51
Q

what are the three external structures that can extend beyond the cell envelope?

A

pili, fimbriae, and flagella

52
Q

what is the function of fimbriae?

A

short, thin, hairlike appendages that can mediate attachment to surfaces, assist with motility, and facilitate DNA uptake

53
Q

what are the functions of sex pili?

A

genes for formation are found on plasmids
required for conjugation

54
Q

what are the flagella?

A

threadlike, locomotor appendages that extend outward from the plasma membrane and cell wall

55
Q

what are the functions of flagella?

A

motility and swarming behavior
attachment to surfaces
may be virulence factors

56
Q

what are the three parts of the ultrastructure?

A

filament, basal body, and hook

57
Q

what are the patterns of flagella distribution?

A

monotrichous
polar flagellum
amphitrichous
lophotrichous
peritrichous

58
Q

monotrichous

A

one flagellum

59
Q

polar flagellum

A

flagellum at end of the cell

60
Q

amphitrichous

A

one flagellum at each end of the cell

61
Q

lophotrichous

A

cluster of flagella at one or both ends

62
Q

peritrichous

A

spread over entire surface of the cell

63
Q

chemotaxis

A

move toward chemical attractants such as nutrients, away from harmful substances

64
Q

what do bacteria move in response to?

A

temperature, light, oxygen, osmotic pressure, and gravity

65
Q

which direction rotation causes forward motion (run)?

A

counterclockwise

66
Q

which direction rotation causes the cell to stop and tumble?

A

clockwise

67
Q

spirochete motility

A

multiple flagella form axial fibril which winds around the cell
remain in periplasmic space inside outer sheath
corkscrew shape exhibits flexing and spinning movements

68
Q

twitching motility

A

pili at ends of cell
short, intermittent, jerky motions
cells are in contact with each other and surface

69
Q

gliding motility

A

smooth movements

70
Q

what are bacterial endospores?

A

complex, dormant structures formed by some bacteria in various locations within the cell

71
Q

what are bacterial endospores resistant to?

A

heat, radiation, chemicals, desiccation

72
Q

what is the structure of an endospore?

A

spore is surrounded by thin covering called exosporium
thick layers of protein form the sore coat
the cortex beneath the coat is made of thick peptidoglycan
the core has nucleoid and ribosomes

73
Q

sporulation process

A
  1. DNA replicates
  2. Membranes form around the DNA
  3. Forespore forms additional membranes
  4. Protective cortex forms around the spore
  5. Protein coat forms around the cortex
  6. Spore is released
74
Q
A

Vet Microbio (12 decks)

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