prokaryotic cell structure Flashcards

1
Q

common features in prokaryotes and eukaryotes

A
  • plasma membrane
  • DNA
  • cell wall (plant, fungal, almost all bacteria)
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2
Q

most common bacterial cell shapes

A
  • coccus (circle)
  • coccobacillus (rod)
  • vibrio (comma)
  • bacillus (long)
  • spirillium (helical)
  • spirochete (long and helical)
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3
Q

dividing bacteria

A
  • can stay together for a period of time
  • in pairs (diplococcus, break off after next division)
  • in a chain (streptococci, associated for a longer time, more divisions occur)
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4
Q

tetrad

A
  • alternate orientation of plane of division so 4 bacteria stay together
  • break up after 4
    e.g. micrococcus
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5
Q

cyanobacteria

A
  • divide alternately to create single layer mats
  • can float in water and photosynthesise
    e.g. Merismopedia spp.
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6
Q

sarcinae

A
  • alternate planes of division to form clumps of 8
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7
Q

ununiform division

A
  • divide in random directions and stay together until clump gets too big, so break off and start dividing
    e.g. S. aureus
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8
Q

structure of a prokaryote

A
  • cell membrane (+cell wall)
  • cytoplasm with inclusions
  • external structures
    (capsules, flagella, pili)
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9
Q

cell wall

A
  • outside cell membrane in most
  • some lack cell wall e.g. mycoplasmus
  • peptidoglycan
  • maintains shape of cell (no cytoskeleton)
  • prevents cell from osmosis by stopping too much water diffusing in
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10
Q

peptidoglycan

A
  • alternating sugars to create strands
  • N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
  • crosslinked with tetrapeptide chains to create strong layers
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11
Q

teichoic acid

A
  • in cell wall of gram-positive bacteria
  • glycerol, phosphates, ribitol (sugar alcohol)
  • projects on/through peptidoglycan layer
  • involved in movement of ions in/out cell
  • bacteriophages can attach on
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12
Q

outer membrane

A
  • gram-negative bacteria only
  • outside peptidoglycan layer
  • porin proteins form channels through outer membrane for transport
  • surface antigens and receptors for cell recongition
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13
Q

periplasmic space

A
  • gap between peptidoglycan layer and outer membrane in gram-negative bacteria
  • contains digestive enzymes
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14
Q

ribosomes

A
  • all free in cytoplasm
  • polyribosomes = chains of ribosomes
  • 70s (80s in eukaryotes)
  • antibiotics including streptomyocin and erythromyocin bind specifically to 70s ribosome, disrupting bacterial protein synthesis but not eukaryotic
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15
Q

pili

A
  • short hollow projections
  • conjugation- gene transfer
  • attachment to surfaces (host invasion)
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16
Q

inclusions

A
  • glycogen or polyphosphate storage granules (energy store)
  • gas or lipid vesicles (storing energy or regulating buoyancy)
17
Q

flagellum

A
  • for movement
  • helically coiled
  • thinner than eukaryotic flagella, ~20nm diameter
18
Q

capsule/slime layer

A
  • covers antigens on cell surface so can help evade host immune system
19
Q

cell membrane

A
  • separates cytoplasm from exterior
  • phospholipid bilayer, proteins including transporters
20
Q

nucleoid

A
  • nuclear region
  • DNA, usually one circular chromosome
    e.g. vibrio cholerae has one large one small chromosome
  • smaller circular plasmids holding extrachromosomal non-essential DNA
21
Q

storage granules in biotechnology

A

e.g. PHB granules, biodegradable plastic
parasporal BT crystal, insecticide (very selective)
suflur globules, carboxysomes

22
Q

endospores

A
  • resistant resting structure
    e.g. in Bacillus and Clostridium spp.
  • allows bacteria to survive inhospitable conditions
  • protected against heat, UV, desiccation by spore coat
  • one spore per bacterium triggered when nutrients start to die out
  • mother cell deteriorates
  • when conditions improve, spore germinates
23
Q

monotrichous (flagella)

A

single polar flagellum

24
Q

lophotrichous (flagella)

A

multiple polar flagella

25
Q

amphitrichous (flagella)

A

one flagella at each end

26
Q

peritrichous (flagella)

A

flagella all over surface

27
Q

atrichous (flagella)

A

no flagella