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ABS > Micro 1- cell structure and classification > Flashcards

Micro 1- cell structure and classification Flashcards

1
Q

creation of the three domain system

A

developed by worse in 1978, based on sequence of nucleotides in rRNA

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2
Q

what are the 3 domains

A
  • eukarya (animals, plants, fungi, protists)
  • bacteria
  • archaea
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3
Q

vertical gene transfer

A

passed down generation to generation

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4
Q

horizontal gene transfer

A

occurs within the community of early cells (not associated with offspring)

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5
Q

important characteristics of prokaryote

A

-one circular chromosome, not in a membrane
-no histones
-no organelles
-divides by binary fission
cell walls: peptidoglycan in bacteria, pseudomurein in archaea

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6
Q

important characteristics of eukaryotes

A
  • paired chromosomes in nuclear membrane
  • histones
  • organelles
  • polysaccaride cell walls, when present
  • divides by mitosis
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7
Q

size, shape, and arrangement of bacterial cells

A

average size: 0.2 to 2.0 um diameter

  • most bacteria are monomorphic (single shape)
  • a few are pleomorphic (many shapes)
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8
Q

list of shapes of cells

A
  • bacillus
  • coccus
  • spiral
  • star-shapes
  • rectangular
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9
Q

bacillus

A

rod shaped

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10
Q

coccus

A

spherical

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11
Q

3 types of spiral shapes

A

vibrio- slightly curved

spirillum- helical, rigid

spirochete- helical, flexible

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12
Q

when cells are arranged in pairs

A

diplococci, diplobacilli

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13
Q

when cells are arranged in chains

A

streptococci, streptobacilli

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14
Q

when cells are arranged in clusters

A

staphylococci

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15
Q

when cells are arranged in groups of four

A

tetrads

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16
Q

when cells are arranged in tubelike groups of eight

A

sarcinae

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17
Q

list of structures external to the cell wall

A
  • glycocalyx
  • flagella
  • axial filaments
  • fimbriae
  • pili
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18
Q

glycocalyx

A

external to cell wall, viscous, gelatinous polymer made of polysaccaride and/or polypeptide

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19
Q

two types of glycocalyx

A
  • capsule: neatly organized and firmly attached

- slime layer: unorganized and firmly attached

20
Q

how does glycocalyx contribute to virulence

A
  • capsules prevent phagocytosis (by WBCs)

- extracellular polymeric substances (EPS) helps form biofilms

21
Q

flagella

A

filamentous appendages external of the cell

  • propel bacteria
  • made of protein flagellin (rotates around hook)
22
Q

3 parts of flagella

A
  1. filament
  2. hook
  3. basal body (this attachment different in gram- or gram+)
23
Q

what does flagella allow bacteria to do

A

flagella allow bacteria to move towards or away from stumble (taxis)

  • chemotaxis for chemical stimulus
  • phototaxis for light stimulus
24
Q

axial filaments

A

endoflagella

  • found in spirochetes
  • anchored at one end of a cell and extend throughout organism
    ex: treponema pallidum
25
Q

axial filaments used to

A

rotation causes cell to move like corkscrew

ex: treponema pallidum

26
Q

fimbriae

A

hair like appendages that allow for attachment

  • adhere to surfaces
  • involved in forming biofilms
27
Q

example of how fimbriae work

A

in neisseria gonorrhoeae, fimbriae helps it colonize mucous membranes- allows this organism to be virulent because it can adhere

28
Q

fimbriae versus flagella

A

similar but fimbriae is shorter, thinner, and straighter

29
Q

pili versus fimbriae

A

pili usually longer than fimbriae

30
Q

pili

A

-one or two per cell, involved in motility (gliding and twitching)

31
Q

pili: gliding vs. twitching

A
  • gliding: myxobacteria (smooth)

- twitching: pseudomonas aeruginosa, neisseria gonorrhoeae and some strains of E. coli

32
Q

conjugation pili

A

are involved in DNA transfer from one cell to another

  • antibiotic resistance
  • digest medium more efficiently
33
Q

purposes of the cell wall

A
  • protects the cell membrane
  • prevents osmotic lysis
  • maintains shape of bacterium (semi-rigid structure)
  • serves as point of anchorage for flagella
  • contributes to pathogenicity
34
Q

cell wall in bacteria

A

made of peptidoglycan (sugar and protein)

complex, semi-rigid structure

35
Q

peptidoglycan is

A

a polymer of a repeating disaccharide in rows

-NAG and NAM (2 types of sugars involved)

36
Q

linkage in peptidoglycan

A

rows are linked by polypeptides

  • tetrapeptide side chains
  • peptide cross bridges
37
Q

how does penicillin affect linkage in peptidoglycan

A

penicillin interferes with final linking and results in weakened cell wall and cell undergoes lysis

38
Q

gram + cell wall

A
  • thick peptidoglycan

- teichoic acids

39
Q

gram - cell wall

A

thin peptidoglycan

  • outer membrane (2nd cell membrane)
  • periplasmic space
40
Q

gram + cell:

composition of teichoic acids

A
  • lipoteichoic acid and wall teichoic acid
  • carry a negative charge
  • regulate movement of cations
  • provide antigenic specificity
41
Q

gram - cell:

3 parts of outer membrane

A
  1. lipoproteins
  2. phospholipids
  3. lipopolysaccharides (LPS)
42
Q

what does the outer membrane of gram - cell do

A
  • protects from phagocytosis and complement

- provides barrier to antibiotics and lysozymes

43
Q

LPS- lipopolysaccharides in gram - outer membrane have

A
  • O polysaccharide: antigen recognizing molecule

- lipid A: endotoxin- causes symptoms of fever, etc.

44
Q

gram staining mechanism crystal violet

A

in gram +, alcohol dehydrates peptidoglycan, CVI crystals do not leave
in gram -, alcohol dissolves outer membrane and leaves holes in peptidoglycan, CVI washes out, cells are colorless, safranin added to stain cells

45
Q

steps of gram stain

A
  1. crystal violet purple dye
  2. iodine (mordant)
  3. alcohol wash (decolorization)
  4. safranin (counterstain)
46
Q

atypical cell walls stain

A

because gram stain not effective, use acid-fast cell wall stain (carbolfuchsin)
example organisms:
-mycobacterium
-nocardia

47
Q

acid-fast cell walls

A
  • no cell walls or very little material

- waxy lipid (mycelia acid) bound to peptidoglycan

ABS (31 decks)

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