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Microbiology - Unit 1 - Zach H. > Lecture 2: Prokaryotic Cell Structure and Function 1 > Flashcards

Lecture 2: Prokaryotic Cell Structure and Function 1 Flashcards

1
Q

Comparison between prokaryotes and eukaryotes are in my handwritten notes.

A

Know them well for the exam.

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2
Q

What dictates the shape of bacteria?

A

Genome

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3
Q

True or False:

Most bacteria are not monomorphic.

A

False - most bacteria are monomorphic

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4
Q

What is the average size of a bacteria?

A

0.2 - 1.0 micrometers x 2 - 8 micrometers

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5
Q

What does peritrichous mean?

A

It refers to flagella being all the way around the bacterium.

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6
Q

What are the 3 shapes that bacteria can take?

A
  • Bacillus (rod-shaped)
  • Coccus (spherical)
  • Spiral
    • spirillum - one or more twists
    • vibrio - curved rod
    • spirochete - flexible, helical spirals
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7
Q

What are the 3 sub-classifications of the basic bacterium shape Sprial?

A
  • Spirillum -> one or more twists
  • Vibrio -> curved rod
  • Spirochete -> flexible, helical spirals
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8
Q

Name two unusually shaped prokaryotes (that are archaea).

A
  • Stella (star-shaped bacteria)
  • Haloarcula, a genus of halophilic archaea (rectangular bacteria)
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9
Q

What is a cluster of cocci bacteria called?

A

Staphylococci

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10
Q

What is a chain of cocci or bacilli bacteria called, respectively?

A
  • Streptococci
  • Streptobacilli
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11
Q

What is a pair of cocci or bacilli bacteria called, respectively?

A
  • Diplococci
  • Diplobacilli
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12
Q

What does a pleomorphic organism refer to?

A

An organism that is variable in shape.

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13
Q

What is a mycelium?

A

A network of long, multinucleate filaments.

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14
Q

True or False:

Smaller cells have a larger surface area/volume ratio.

A

True

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15
Q

List all of the common bacterial structures that you can.

A
  • plasma membrane
  • gas vacuole
  • ribosomes
  • inclusions
  • nucleoid
  • periplasmic space
  • cell wall
  • capsules and slime layers
  • fimbriae and pili
  • flagella
  • endospores
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16
Q

What structures make up the bacterial cell envelope?

A
  • plasma membrane
  • cell wall
  • layers outside the cell wall (e.g., slime layer)
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17
Q

True or False:

The plasma membrane is an absolute requirement for all living organisms.

A

True

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18
Q

What is a gas vacuole?

A

An inclusion that provides buoyancy for floating in aquatic environments.

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19
Q

What are inclusions?

A

Storage of carbon, phosphate, and other substances.

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20
Q

What is a nucleoid?

A

Localization of genetic material (DNA).

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21
Q

What is the periplasmic space of typical gram-negative bacteria? What about gram-positive?

A
  • Gram-Negative Bacteria:
    • contains hydrolytic enzymes and binding proteins for nutrient processing and uptake.
  • Gram-Positive Bacteria:
    • may be smaller or absent
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22
Q

What does the cell wall protect the bacteria against?

A
  • Protection from osmotic stress
  • Helps maintain cell shape
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23
Q

What is the function of capsules and slime layers in bacteria?

A
  • resistance to phagocytosis
  • adherence to surfaces
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24
Q

What is the function of fimbriae and pili of bacteria?

A
  • Fimbriae and Pili
    • attachment to surfaces
    • bacterial conjugation and transformation
    • twitching motility
    • gliding motility
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25
Q

What are flagella used for in bacteria?

A
  • Swimming and Swarming Motility
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26
Q

What does the bacteria use an endospore for?

A
  • Survival under harsh environmental conditions
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27
Q

Do bacterial membranes lack sterols (like cholesterol)?

A

Yes - but DO contain hopanoids, which are sterol-like molecules (e.g., bacteriohopanetetrol).

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28
Q

What do hopanoids found in the bacterial membrane function to do?

A
  • stabilize bacterial membrane
  • found in petroleum
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29
Q

What is an environmental conditions example that determines lipid composition in bacterial and eukaryotic membranes?

A

Temperature

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30
Q

True or False:

Many bacteria have plasma membrane infoldings.

A

True

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31
Q

What makes Archaeal membranes very distinctive from Bacteria and Eukaryotes?

A
  • composed of lipids that differ chemically
    • Bacterial or Eukaryotic Lipids:
      • Ester Bonds
      • 2 Hydrocarbons attached to glycerol
    • Archaeal Lipids:
      • Ether Bonds
      • Branched molecules
      • Tetraethers (some)
  • some have a monolayer structure instead of a bilayer structure
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32
Q

What type of diethers are bilayer Archaeal membranes composed of?

A
  • Bilayer composed of C20 Diethers
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33
Q

What type of tetraethers are monolayer Archaeal membranes composed of?

A
  • Monolayer composed of C40 Tetraethers
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34
Q

What is the function of the plasma membrane?

A
  • encompasses the cytoplasm
  • selectively permeable barrier
  • interacts with external environment
    • receptors for detection of an response to chemicas in surroundings
    • transport systems
    • metabolic processes
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35
Q

What does the cytoplasm of Bacteria and Archaea consist of.

A
  • Substance in which nucleoid, ribosomes, inclusion bodies, plasmids, and cytoskeletal filaments are suspended.
  • LACKS organelles bound by unit membranes
  • Composed largely of water
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36
Q

What is the cytoplasm of Bacteria and Archaea largely composed of?

A

Water

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37
Q

True or False:

Homologs of all three Eukaryotic cytoskeletal elements have been identified in Bacteria.

A

True

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38
Q

What are the best studied examples of bacterial cytoskeletal proteins?

A
  • FtsZ - many bacteria
    • function: forms ring during septum formation in cell division
  • MreB - found in bacilli, NOT in cocci
    • function: maintains shape by positioning peptidoglycan synthesis machinery
  • CreS - rare
    • function: maintains curve shape
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39
Q

In what type of bacteria is plasma membrane infoldings typically observed?

A
  • observed in many photosynthetic bacteria
  • observed in many bacteria with high respiratory activity
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40
Q

What is anammoxosome in Planctomycetes, and what is its function?

A

Organelle - site of anaerobic ammonia oxidation

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41
Q

List several organic and inorganic material that is stored in granules of inclusions.

A
  • Storage of nutrients, metabolic end products, energy, building blocks.
  • Glycogen Storage
  • Carbon Storage
    • poly-beta-hydroxybutyrate (PHB)
    • glycogen
  • Phosphate - polyphosphate granules (Volutin)
  • Amino Acids - cyanophycin granules
  • Sulfur Granules
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42
Q

In what type of organism are gas vacuoles found?

A

Found in aquatic, photosynthetic Bacteria and Archaea.

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43
Q

What does cytoskeletal protein, MamK, function to do?

A

Helps form magnetosome chain.

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44
Q

What are magnetosomes?

A
  • Other inclusions
  • Found in aquatic bacteria
  • Magnetite particles (iron) for orientation in Earth’s magnetic field
  • Used by organisms to orient themselves so they know which way is up or down
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45
Q

What are microcompartments?

A
  • NOT bound by membranes but compartmentalized for a specific function.
  • Carboxysomes - CO2 fixing bacteria
    • contain the enzyme ribulose-1,5,-bisposphate carboxylase (Rubisco), enzyeme used for CO2 fixation
46
Q

What is the bacterial ribosomal RNA size?

A
  • Bacterial and ARchaea Ribosome = 70S
  • 16S small subunit
  • 23S and 5S in large subunit
47
Q

What is the size of the Eukaryotic ribosomal RNA subunit?

A

80S

48
Q

What are the characteristics of the nucleoid?

A
  • Usually not membrane bound (few exeptions)
  • Location of chromosome and associated proteins
  • Usually 1 closed circular, double-stranded DNA molecule
  • Supercoiling and nucleoid proteins (different from histones) aid in folding
49
Q

What are the characteristics of Prokaryotic chromosomes?

A
  • Usually a circular, double-stranded DNA molecule
  • Usually only 1
  • Looped and coiled extensively
50
Q

What are plasmids?

A
  • extrachromosomal DNA
    • found in bacteria, archaea, some fungi
    • usually small, closed circular DNA molecules
  • exist and replicate independently of chromosome
    • episomes - may integrate into chromosome
    • inherited during cell division
  • contain few genes that are non-essential
    • confer selective advantage to host (e.g., drug resistance)
  • classification based on mode of existence, spread, and function
51
Q

Which type of plasmids are the largest?

A

Metabolic Plasmids (carry genes for enzymes)

52
Q

Which type of plasmid is the smallest?

A

Col Plasmids (produce bacteriocins, substances that destroy closely related species)

53
Q

What type of plasmid transfers DNA from one cell to another?

A

Conjugative Plasmids

54
Q

Which type of plasmid carries antibiotic-resistance genes?

A

R Plasmids

55
Q

What is the function of Virulence Plasmids?

A

To carry virulence genes.

56
Q

Does gram-positive or gram-negative cells have a thick peptidoglycan layer?

A

Gram-Positive

57
Q

What color does Gram-Positive Bacterial cells stain?

A

Stain Purple

58
Q

What color does Gram-Negative Bacterial cells stain?

A

Stain Pink or Red

59
Q

Does Gram-Negative Bacterial Cells have a thick or thin peptidoglycan layer?

A

Thin peptidoglycan and outer membrane.

60
Q

What are the functions of the cell wall?

A
  • Maintains shape of the bacterium
    • almost all bacteria cell from osmotic lysis
  • Helps protect cell from osmotic lysis
  • Helps protect from toxic materials
  • May contribute to pathogenicity
61
Q

Explain the peptidoglycan structure?

A
  • Meshlike polymer of identical subunits forming long strands.
  • Chains of peptidoglycan subunits are joined by cross-links (covalent bonds) between the peptides.
  • Meshlike polymer of identical subunits forming long strands.
    • two alternating sugars
      • N-acetylglucosamine (NAG)
      • N-acetylmuramic acid
    • alternating D- and L-amino acids
62
Q

What are the characteristics of gram-positive cell walls.

A
  • composed primarily of peptidoglycan
  • may also contain teichoic acids (negatively charged)
    • help maintain cell envelope
    • protect from environmental substances
    • may bind to host cells
  • some gram-positive bacteria have layer of proteins on surface of peptidoglycan
63
Q

Which type of acid connects the cell wall to the plasma membrane?

A

lipoteichnoic acid

64
Q

True or False:

Teichoic acid is like rebar in a slap of concrete.

A

True

65
Q

True or False:

Peptidoglycan strands do not have a helical shape.

A

False - peptidoglycan strands have a helical shape.

66
Q

Why are peptidoglycan chains crosslinked by peptides?

A
  • For Strength
    • interbridges may form
    • peptidoglycan sacs - interconnected networks
    • various structures occur
67
Q

What type of peptide interbridge connects peptidoglycan strands in S. aureus? Also, between which amino acids does it link?

A
  • 5-Glycines
  • D-Alanine and L-Lysine
68
Q

What peptidoglycan strands are crosslinked in E. coli?

A

D-Alanine to DAP

69
Q

What is the characteristic of the periplasmic space of gram positive bacteria?

A
  • lies between plasma membrane and cell wall and is smaller than that of gram-negative bacteria
  • periplasm has relatively few proteins
  • enzymes secreted by gram-positive bacteria are called exoenzymes
    • aid in degradation of large nutrients
70
Q

Do gram positive bacterial cells have small or large periplasmic spaces?

A

small periplasmic space

* gram negative bacterial cells have a bigger periplasmic space *

71
Q

What are the characteristics of gram-negative cell walls?

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 lipopolysaccharide (LPS)
  • NO teichoic acids
  • peptidoglycan is 5-10% of cell wall weight
  • periplasmic space differes from that in gram-positive cells
    • may constitute 20-40% of cell volume
    • many enzymes present in periplasm
      • hydrolytic enzymes, transport proteins and other proteins
  • outer membrane lies outside that thin peptidoglycan layer
  • Braun’s lipoproteins connect outer membrane to peptidoglycan
  • other adhesion sites reported
72
Q

Which 3 components make up lipopolysaccharide (LPS)?

A
  • lipid A
  • core polysaccharide
  • O side chain (O antigen)
73
Q

Is lipid A embedded in the outer membrane or does it extend out from the cell?

A

Lipid A embedded in outer membrane.

74
Q

Does the core polysaccharide and the O side chain extend out from the cell or is it embedded in the outer membrane?

A

Core polysaccharide, O side chain extend out from the cell.

75
Q

Which part of the LPS can act as a endotoxin?

A

Lipid A portion serves as the endotoxin.

76
Q

Why is LPS so important?

A
  • contributes to 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)
77
Q

Why is the gram-negative outer membrane more permeable than the plasma membrane?

A
  • Due to presence of porin proteins and transporter proteins.
    • porin proteins form channels to let small molecules (600-700 daltons) pass
78
Q

What does a hypotonic environment consist of?

A
  • solute concentration outside the cell is less than inside the cell
  • water moves into cell and cell swells
  • cell wall protects from lysis
79
Q

What does a hypertonic environment consist of?

A
  • solute concentration outside the cell is greater than inside
  • water leaves the cell
  • plasmolysis occurs
80
Q

What does penicillin inhibit?

A

Penicillin inhibits peptidoglycan synthesis.

81
Q

What bond does lysozyme break in the cell wall?

A

Lysozyme breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid.

82
Q

Which type of organisms that lose a cell wall may survive in isotonic environments?

A
  • protoplasts
  • spheroplasts
  • mycoplasma
    • does not produce a cell wall
    • plasma membrane more resistant to osmotic pressure
      • because it has cholesterol in its cell membrane, which is normally not characteristic of bacteria
83
Q

Do Archaeal cell walls lack peptidoglycan?

A

Yes, some have pseudopeptidoglycan, also called pseduomurein.

84
Q

Which components are found outside of the cell wall?

A
  • outermost layer in the cell envelope
  • glycocalyx
    • capsules and slime layers
    • S layers
  • aid in attachment to solid surfaces
    • e.g., biofilms in plants and animals
85
Q

What are capsules usually composed of?

A

Polysaccharides

86
Q

True or False:

Capsules are well organized and not easily removed from the cell.

A

True

87
Q

What are the protective advantages of a capsule?

A
  • resistant to phagocytosis
  • protect from desiccation
  • exclude viruses and detergents
88
Q

Are capsules visible under the light microscope?

A

Yes

89
Q

What are the characteristics of slime layers?

A
  • similar to capsules except diffuse, unorganized and easily removed
  • slime may aid in motility
90
Q

What are the characteristics of the S layes?

A
  • Regularly structured layers of protein or glycoprotein that self-assemble
    • in gram-negative bacteria the S layer adheres to outer membrane
    • in gram-positive bacteria it is associated with the peptidoglycan surface
  • 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
    • S layer spontaneously associates
91
Q

The biofilm layer, S layer, and slime layers are all important for attachment; so are fimbriae.

A

Important to Know for the exam.

92
Q

True or False:

The external structures extend beyond the cell envelope in bacteria.

A

True

93
Q

What do external structures of the bacterial cell function to do?

A
  • Extend beyond the cell envelope in bacteria
  • Function in protection, attachment to surfaces, horizontal gene transfer, cell movement
    • pili and fimbriae
    • flagella
94
Q

What are fimbriae?

A
  • short, thin, hairlike, proteinaceous appendages (up to 1,000/cell)
  • can mediate attachment to surfaces
  • some (type IV fimbrieae) required for twitching motility or gliding motility that occurs in some bacteria
95
Q

What are sex pili?

A
  • longer, thicker, and less numerous (1-10/cell)
  • genes for formation found in plasmids
  • required for conjugation (mating)
96
Q

What are flagella?

A
  • threadlike, locomotor appendages extending outward from plasma membrane and cell wall
  • Functions:
    • motility and swarming behavior
    • attachment to surfaces
    • may be virulence factors
97
Q

What are the three parts of flagella?

A
  • Filament
    • extends from cell surface to the tip
    • hollow, rigid cylinder of flagellin protein
  • Hook
    • links filament to basal body
  • Basal Body
    • series of rings that drive flagellar motor
98
Q

What are bacterial flagella?

A
  • thin, rigid protein structures that cannot be observed with bright-field microscope unless specially stained
  • ultrastructure composed of three parts
  • pattern of flagellation varies
99
Q

What are the different patterns of flagella distribution?

A
  • monotrichous - one flagellum
  • polar flagellum - flagellum at end of cell
  • amphitrichous - one flagellum at each end of cell
  • lophotrichous - cluster of flagella at one or both ends
  • peritrichous - spread over entire surface of cell
100
Q

What type of directed movement do Bacteria and Archaea have?

A
  • flagellar movement
  • spirochete motility
  • twitching motility
  • gliding motility
101
Q

What is chemotaxis?

A
  • move toward chemical attractants such as nutrients, away from harmful substances
    • movement toward a chemical attractant or away from a chemical reprellent
    • changing concentrations of chemical attractants and chemical repellents bind chemoreceptors of chemosensing system
    • in presence of attractant tumbling frequency is intermeittently reduced and runs in direction of attractant are longer
    • behavior of bacterium is altered by temporal concentration of chemical
    • chemotaxis away from repellent involves similar but oppostie responses
102
Q

What is flagellar movement good for?

A

liquids

103
Q

What are gliding and twitching motility good for?

A

hard surfaces

104
Q

What is spirochete motility good for?

A

viscous material because it has more of a corkscrew movement

105
Q

What is bacterial flagellar movement?

A
  • Flagellum rotates like a propeller
    • very rapid rotation up to 1100 revolutions/sec
    • in general, counterclockwise (CCW) rotation causes forward motion (run)
    • in general, clockwise rotation (CW) disrupts run causing cell to stop and tumble
106
Q

What does MotA and MotB do in the mechanism of flagellar movement?

A

MotA and MotB create a channel through which protons can flow. This causes the flagellum to rotate.

107
Q

What is spirochete motility?

A
  • multiple flagella form axial fibril which winds around the cell
  • flagella remain in periplasmic space inside outer sheath
  • corkscrew shape exhibits flexing and spinning movements
108
Q

What is twitching and gliding motility?

A
  • may involve type IV pili and slime
  • twitching
    • pili at ends of cell
    • short, intermittent, jerky motions
    • cells are in contact with each other and surface
  • gliding
    • smooth movements
109
Q

What is a bacterial endospore?

A
  • complex, dormant structure formed by some bacteria
  • various locations within the cell
  • resistant to numerous environmental conditions
    • heat
    • radiation
    • chemicals
    • desiccation
110
Q

What makes an endospore so resistant?

A
  • calcium (complexed with dipicolinic acid)
  • small, acid-soluble, DNA-binding proteins (SASPs)
  • dehydrated core
  • spre coat and exosporium protect
  • DNA repair enzymes
111
Q
A

Microbiology - Unit 1 - Zach H. (4 decks)

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