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Microbiology > ch 3 bacterial cell structure > Flashcards

ch 3 bacterial cell structure Flashcards

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Biology 101 flashcards
1
Q

cocci

A

spheres that can be single or can be associated in arrangements that is useful for identification

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2
Q

diplococci

A

arise when cocci divide and remain together to form pairs

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3
Q

streptococci

A

divide on 1 plane to form long chains

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4
Q

staphylococci

A

divide in random planes making grape-like clusters

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5
Q

bacilli

A

rod shaped
differ considerably in their length-to-width ratio
coccobacilli - short and wide

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6
Q

vibrios

A

comma shaped

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7
Q

spirilla

A

rigid spiral shaped

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8
Q

spirochetes

A

flexible sprial-shaped

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9
Q

mycelium

A

network of long filaments (hyphae)

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10
Q

pleomorphic

A

organisms that are variable in shape

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11
Q

size-shape relationship

A

cells want a high surface area-to-volume ratio
- increases efficiency of nutrient uptake and diffusion of molecules within a cell
- large size and odd shape may be protective mechanisms from predation

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12
Q

cell envelope

A

plasma membrane and all the surrounding layers external to it

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13
Q

plasma membrane

A

most important of cell envelope
encompasses the cytoplasm and defines the cell
responsible for much of the cell’s relationship with the outside world
- selectively permeable barrier
- detects and responds to surrounding chemicals
- transport systems used for nutrient uptake
- metabolic processes

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14
Q

amphipathic

A

structurally asymmetric with polar and nonpolar ends

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15
Q

hopanoids

A

hydrophobic rigid planar structure similar to cholesterol

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16
Q

functional membrane microdomains

A

platforms for protein complex assemble

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17
Q

bacterial lipids

A
  • plasma membrane is mainly composed of phospholipids
  • have hopanoids
  • distort the bilayer, which impacts the fluidity and shape in the membrane region
  • form functional membrane microdomains
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18
Q

six macronutrients required by bacterial cells

A

carbon
oxygen
hydrogen
nitrogen
sulfur
phosphorus

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19
Q

growth factors

A

organic compounds that must be supplied in the diet for growth because they are essential cell components or precursors of such components and cannot be synthesized by the organism

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20
Q

4 transport mechanisms

A

passive diffusion
facilitated diffusion
primary and secondary active transport
group translocation

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21
Q

passive diffusion

A

molecules move from a region of higher conc to one of lower conc
- large conc gradient required for adequate nutrient uptake
- H2O, O2, CO2 easily cross the plasma membrane

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22
Q

facilitated diffusion

A

movement across the plasma membrane with the assistance of transport proteins that are either channels or carriers
- direction of movement is from high to low conc
- no energy required

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23
Q

active transport

A

transport of molecules against the conc gradient
- energy dependent process

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24
Q

group translocation

A

energy dependent transport that chemically modifies the molecules as it is brought into the cell
- phosphoenolpyruvate: sugar phosphotransferase system

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25
Q

why is uptake of ferric iron difficult

A

it is very insoluble

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26
Q

sideophores

A

secreted by bacteria and complex with ferric iron for transport into cell

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27
Q

cell wall

A

layer that lies just outside the plasma membrane
- helps maintain cell shape
- protect the cell from osmotic lysis
- protect the cell from toxic substances
- contribute to the ability of a pathogen to cause disease

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28
Q

peptidoglycan

A

rigid structure lying outside the plasma membrane
crosslinked by peptides for strength

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29
Q

gram positive cell wall

A

stains purple
thick peptidoglycan
may also contain teichoic acids

30
Q

gram negative cell wall

A

stains pink or red
thin peptidoglycan and outer membrane (composed of lipids, lipoproteins, lipopolysaccharides

31
Q

peptide interbridge

A

a short chain of amino acids linking the stem peptide of one peptidoglycan strand to that of another

32
Q

teichoic acids

A

polymers of glycerol or ribitol joined by phosphate groups
- negatively charged
- help create and maintain structure of the cell envelope by anchoring the wall to the plasma membrane
- protect from harmful substances during cell division
- bind to host cells, initiate infectious disease process

33
Q

periplasmic space

A

space btw plasma membrane and cell wall
periplasm occupies this space
- contains enzymes, transport proteins

34
Q

lipopolysaccharide

A

a molecules containing both lipid and polysaccharide found in the outer membrane of the typical gram-negative cell wall
consists of three parts:
- lipid A - buried in outer membrane, contains two glucosamine sugar derivatives
- core polysaccharide - joined to lipid A and is constructed of 10 sugars
- O side chain (O antigen) - polysaccharide chain extending outward from the core

35
Q

functions of LPS

A
  • contributes to the negative charge on the bacterial surface bc the core polysaccharide usually contains charged sugars and phosphate
  • it helps stabilize outer membrane structure because lipid A is a major constituent of the exterior leaflet of the outer membrane
  • it helps crate a permeability barrier
  • helps protect pathogenic bacteria from host defenses
  • lipid A can act as a toxin (endotoxin)
36
Q

porins

A

proteins that form channels across the outer membrane of typical gram-negative bacterial cell walls through which small molecules enter the periplasm
- facilitated transport

37
Q

two step process of transport into a gram-negative cell

A
  1. the solute crosses the outer membrane into the periplasm (by porins)
  2. crosses the plasma membrane
38
Q

plasmolysis

A

water flows out of the cell and the cytoplasm shrivels up
- solute conc outside cell is greater than inside
hypertonic environment

39
Q

lysis

A

water moves into the cell and cell swells and bursts
- solute conc outside cell less than inside the cell
hypotonic solution

40
Q

lysozyme

A

attacks peptidoglycan by hydrolyzing the bond that connects N-acetylmuramic acid with N-acetylglucosamine

41
Q

evidence of protective nature of peptidoglycan

A
  • lysozyme breaks bond btw peptidoglycan
  • penicillin inhibits peptidoglycan synthesis
    when cells treated with either of the above, they lyse in a hypotonic solution
42
Q

mycoplasma

A

lack a cell wall, but plasma membrane more resistant to osmotic pressure

43
Q

extracellular vesicles (EVs)

A

small membrane-bound particles
develop when a membrane buds out, pinches off, and is released from the cell

44
Q

gram positive EV

A

made of the plasma membrane surrounding a small amount of cytoplasm

45
Q

gram negative EV

A

made of LPS containing outer membrane surrounding a sample of periplasm

46
Q

capsules

A

well organized layers that are most often composed of polysaccharides and not easily removed from cell
- helps protect from desiccation, resists phagocytosis from hose, exclude viruses and most hydrophobic toxic materials

47
Q

s-layer

A

a regularly structured layer composed of protein or glycoprotein that lies on the surface of many bacteria and archaea
- like capsules but are easily removed
- look like floor tiles
- “armored” protection for bacteria
in gram negative adheres to outer membrane
in gram positive associates with peptidoglycan

48
Q

s-layer functions

A
  • protect from ion and pH fluctuations, osmotic stress, enzymes, and predation
  • maintains shape and rigidity
  • promotes adhesion to surfaces
  • protects from host defences
  • potential use in nanotechnology
49
Q

protoplast

A

plasma membrane and everything within

50
Q

cytoplasm

A

the material bounded by the plasma membrane

51
Q

cytosol

A

liquid component of cytoplasm

52
Q

cytoskeleton

A

composed of several types of protein filaments
play role in cell division, maintaining cell shape, and positioning and segregating inclusions and plasmid DNA

53
Q

intracytoplasmic membrane

A

plasma membrane infoldings
- observed in many photosynthetic bacteria
- observed in many bacteria with high respiratory activity
- may be aggregates of spherical vesicles

54
Q

inclusions

A

common in all cells
formed by the aggregation of organic and inorganic substances
primary function - segregate cellular components so they do not diffuse freely in the cytoplasm
function as storage sites, locations to sequester enzymatic reactions or guides for cell movement
can take the form of granules, crystals, globules

55
Q

gas vacuoles

A

type of inclusion
involved in bacterial movement
provide buoyancy to aquatic bacteria
made of aggregates of hollow, cylindrical gas vesicles

56
Q

ribosomes

A

site of protein synthesis

57
Q

nucleoid

A

ellipsoidal region that contains the cell’s chromosome and numerous proteins
usually not membrane bound

58
Q

plasmids

A

double stranded dna molecules that can exists independently of the chromosome
- carry genes that can confer a selective advantage in some situations

59
Q

episomes

A

plasmids that can integrate into the chromosome

60
Q

fimbriae

A

short, think, hairlike protein appendages that can mediate attachment to surfaces, motility

61
Q

sex pili

A

longer, thicker, less numerous
genetically encoded on plasmids
required for conjugating
- motility

62
Q

flagella

A

threadlike, locomotor appendages extending outward from plasma membrane and cell wall
motility, attachment to surfaces, virulence factors

63
Q

3 parts of flagella

A

filament - extends from cell surface to tip
basal body - embedded in cell envelope
hook - short curved segment

64
Q

chemotaxis

A

movement towards chemical attractants and away from repellents

65
Q

two types of flagellar swimming movement

A

run - moves the cell from one spot to another
tumble - reorients the cell

66
Q

swarming motility

A

type of group behavior in which the cells move in unison across a moist surface

67
Q

spirochete motility

A

undulation of the entire cell
multiple flagella form axial fibril which winds around the cell

68
Q

twitching motility

A

short, intermittent, jerky motions of up to several micrometers in length and is normally seen on moist surfaces
- does not involve flagella
- pili at ends of cell

69
Q

gliding motility

A

smooth movements that do not require appendages
slime secretion to reduce friction

70
Q

endospores

A

complex, dormant structure formed by some bacteria
form in response to nutrient depletion
resistant to numerous environmental conditions
- heat, UV radiation, gamma radiation, chemical disinfectants, and desiccation

71
Q

endospore structures

A

exosporium - thin covering surrounding spore
spore coat - thick layers of protein
cortex - thick peptidoglycan
core - has nucleoid and ribosomes

72
Q

sporulation

A

commences when growth slows die to nutrient limitation
a survival mechanism that allows the bacterium to produce a dormant cell that can persist until nutrients are available and vegetative growth can resume

Microbiology (13 decks)

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