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Microbiology > Ch. 3 - Bacterial Cell Structure > Flashcards

Ch. 3 - Bacterial Cell Structure Flashcards

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1
Q

Pleomorphism

A

•variations in size and shape among cells of a single species

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2
Q

Peptidoglycan

A 
• main component of bacterial cell walls
• A complex of sugars and amino acids
• two types based on Gram stain:
1) gram positive - stain purple; thick
2) gram negative - stain pink; thin
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3
Q

Mycelium

A
  • A possible shape of bacteria

* network of long, multinucleate filaments

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4
Q

Pleomorphic

A

• organisms that are variable in shape

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5
Q

Smallest bacteria size

A

0.3 micro meters (Mycoplasma)

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6
Q

Average bacteria size

A

1.25 x 2 to 6 micro meters (E. Coli)

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7
Q

Very large bacteria size

A

600 x 80 micro meters (Epulopiscium fishelsoni)

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8
Q

Three general shapes of bacteria

A
  • coccus - spheres, oval, bean-shaped, pointed
  • bacillus - cylindrical
  • spirillum - rigid helix
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9
Q

Bacterial cell organization common features

A
  • cell envelope - 3 layers
  • cytoplasm (plasma membrane)
  • external structures
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10
Q

Bacterial cell envelope 3 layers

A
  • plasma membrane
  • cell wall
  • layers outside cell wall
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11
Q

Bacteria plasma membrane functions

A 
• encompasses the cytoplasm
• selectively permeable barrier
• interacts with external environment
-receptors for detection of and response to chemicals in surroundings
-transport systems
-metabolic processes
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12
Q

Periplasmic space

A
  • found in gram negative bacteria between the plasma membrane and outer membrane
  • sometimes observed between the plasma membrane and cell wall in gram-positive bacteria
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13
Q

Peptidoglycan main components

A

•sugars and amino acids

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14
Q

Coccus

A

• spherical, oval, been shaped, pointed

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15
Q

Bacillus

A

•Cylindrical, Rod shaped

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16
Q

Spirillum

A

• rigid helix

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17
Q

Streptococcus

A

•Long chains of cocci (spherical shapes)

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18
Q

Staphylococcus

A

• divide in random planes to generate irregular, grapelike clumps

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19
Q

Cell wall

A

• layer that lives just outside the plasma membrane

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20
Q

Cell wall functions

A
  • maintains shape of the bacteria
  • helps protect Cell from osmotic lysis
  • helps protect from toxic materials
  • May contribute to pathogenicity
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21
Q

Peptidoglycan structure

A 
• mesh like polymer of identical subunits forming long strands
-2 alternating sugars:
     •N-acetylglucosamine (NAG)
     •N-acteylmuramic acid (NAM)
-alternating D- and L- amino acids
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22
Q

Peptide interbridge

A
  • crosslink sugars together in peptidoglycan structure

* A component of peptidoglycan which connects one sugar polymer to another

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23
Q

Teichoic acid

A
  • found only in gram-positive cell walls
  • extend to surface of the peptidoglycan
  • negatively charged and help give the cell wall it’s negative charge
  • help maintain cell envelope
  • protect from environmental substances
  • made bind to host cells
  • contribute to acidic charge on cell surface of gram-positive
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24
Q

Exoenzymes

A
  • enzymes secreted by gram-positive bacteria

* Aid in degradation of large nutrients, ex: Mucinase, keritinase

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25
Q

Gram-positive cell walls

A
  • composed primarily of peptidoglycan
  • May also contain teichoic acids
  • some have layer of proteins on the surface of peptidoglycan
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26
Q

Gram-negative cell walls

A

• more complex than gram-positive
• consists of a thin layer of peptidoglycan surrounded by an outer membrane
• outer membrane composed of lipids, lipoproteins, and lipopolysaccharides (LPS)
• no techoic acids
• peptidoglycan is 5 to 10% of cell wall wait
• Periplasmic space may constitute 20 to 40% of cell volume
• many enzymes present and periplasm
-hydrolytic enzymes, transport proteins, and others

27
Q

Brauns lipoproteins

A
  • found in gram-negative cell walls

* Connect outer membrane to peptidoglycan

28
Q

Importance of LPS

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 endotoxin (lipid A)
29
Q

Permeability of gram-negative outer membrane

A
  • more permeable then plasma membrane due to presence of porin proteins in transporter proteins
  • porin proteins form channels to let small molecules pass
30
Q

Mechanism of Gram stain reaction

A
  • stain with Violet which is positively charged and attracts to negatively charged bacteria
  • iodine added for dye retention
  • decolorization with ethanol
  • safranin
31
Q

Hypotonic environment

A
  • solute concentration outside the cell is less than inside the cell
  • water moves into cell and cell swells
  • cell wall protects from lysis
32
Q

Hypertonic environment

A
  • solute concentration outside the cell is greater than inside
  • water leaves the cell
  • plasmolysis occurs
33
Q

Capsule

A 
• located outside of the cell membrane in bacterial cells
• well organized and not easily removed from cell
• usually composed of polysaccharides
• visible in light microscope
•advantages:
-resistant to phagocytosis
-protect from desiccation
-exclude viruses and detergents
34
Q

Slime layer

A
  • similar to capsules except diffuse, unorganized and easily removed
  • slime may aid in motility
35
Q

Glycocalyx

A
  • refers to a layer consisting of a network of polysaccharides extending from the surface of the cell
  • can include both capsules and slime layers because they usually are composed of polysaccharides
  • aids in attachment to solid surfaces including tissue surfaces in plants and animal hosts
36
Q

Similarities between eukaryotic and bacterial cell membranes

A
  • bilayer of lipids
  • fluid
  • contains integral proteins
  • composed of primarily of lipids
37
Q

S layer

A
  • regularly structured layers of proteins or glycoprotein that self assemble
  • gram-negative: adheres to outer membrane
  • gram-positive: associated with peptidoglycan surface
38
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 defenses
• potential use in nanotechnology
- S layer spontaneously associates
39
Q

Bacterial cytoplasmic structures

A
  • cytoskeleton
  • Intracytoplasmic membranes
  • inclusions
  • ribosomes
  • Nucleoid and plasmids
40
Q

Protoplast

A

•The plasma membrane and everything within

41
Q

Cytoplasm

A

• The material bounded by the plasma membrane; thus a major part of the protoplast

42
Q

Functions of cytoskeleton proteins

A
  • participate in cell division
  • localize proteins to certain sites in the cell
  • determine cell shape
  • some appear to be unique to bacteria
43
Q

Endospore

A
  • dormant cells formed within a so-called mother cell
  • fascinating bacterial structures only produced by certain members of Bacillus and clostridium (rods) and sporosarcina (cocci)
  • resistant to many very hostile environments
44
Q

Fimbriae

A
  • Aid in motility
  • Aid in the uptake of DNA
  • Aid in attachment to surfaces
45
Q

plasmids

A

• extrachromosomal DNA
-found in bacteria, archaea , some fungi
-usually small, closed circular DNA molecules
• exist and replicate independently of chromosomes
-episomes - may integrate into chromosome
-inherited during cell division
• contain few genes that are nonessential
-confer selective advantage to host
• classification based on mode of existence, spread, and function

46
Q

Plasma membrane functions

A

• selectively permeable barrier: they allow particular ions and molecules to pass either in or out of the cell while preventing movement of others
•metabolic processes:
-respiration
- photosynthesis
-synthesis of lipids and cell wall constituents

47
Q

Ribosome

A

• responsible for protein synthesis

48
Q

Methods of motility for bacteria

A
  • swimming
  • swarming
  • corkscrew movement
  • twitching
  • gliding
49
Q

Fluid Mosaic model

A

• describes the way in which lipids behave in a membrane

50
Q

Bacterial plasma membrane proteins

A 
• peripheral
-loosely connected to membrane
-easily removed
• integral
-amphipathic - embedded within membrane
-Carry out important functions
51
Q

Hopanoids

A
  • similar to our cholesterol
  • stabilizes membrane and makes it stronger
  • found in petroleum
52
Q

Macroelements that help uptake of nutrients

A

•C, H, O, N, P, S
- found in organic molecules such as proteins, lipids, carbs, and nucleic acids
• K, Ca, Mg, and Fe
- cations and serve in variety of roles including enzymes, biosynthesis
• required in large amounts

53
Q

Micronutrients that help uptake of nutrients

A
  • Mn, Zn, Co, Mo, Ni, and Cu
  • required in trace amounts
  • often supplied in water or in media components
  • Ubiquitous in nature
  • serve as enzymes and cofactors
54
Q

Characteristics of growth factors that help uptake of nutrients through barrier

A
  • organic compounds
  • essential cell components that the cell cannot synthesize
  • must be supplied by environment if cell is to survive and reproduce
55
Q

Classes of growth factors

A 
• amino acids
-needed for protein synthesis
• purines and pyrimidines
-needed for nucleic acid synthesis
• vitamins
- function as enzyme cofactors
• heme
-iron-based groups
56
Q

Transport mechanisms of microorganisms

A
  • facilitated diffusion
  • Active transport
  • Group translocation -bacteria and Arcaea
  • endocytosis - bacteria cannot do this
57
Q

Passive diffusion

A
  • molecules move from region of higher concentration to one of lower concentration between the cells interior and exterior
  • H2O, O2, CO2 often move across membranes this way
  • no energy required
58
Q

Facilitated diffusion

A

• similar to passive diffusion
-Direction of movement is from high concentration to low concentration
•Differs from passive diffusion
-uses membrane-bound carrier molecules (permeases)
-smaller concentration gradient is required for significant uptake of molecules
-effectively transports glycerol, sugars, and amino acids

59
Q

Active transport

A 
• Energy required
• move molecules from low to high concentration gradient
• limits how quickly this can happen
• involves carrier proteins (permeases)
• 3 types:
1) ABC Transporters
2) Secondary active transport 
3) group translocation
60
Q

ABC transporters

A

• primary active transporters use ATP
• ATP binding cassette (ABC) transporters
• observed in bacteria, archaea, and eukaryotes
• consist of:
-2 hydrophobic membrane spanning domains
-2 cytoplasmic associated ATP binding domains
-substrate binding domains
• change shape

61
Q

Secondary active transport

A

• major facilitator superfamily (MFS)
• use ion gradients to cotransport substances
- protons
- symport - two substances both move in the same direction
- antiport - two substances move in opposite directions

62
Q

Group translocation

A
  • Energy dependent transport that chemically modified molecule as it is brought into cell
  • Best known translocation system is phosphoenolpyruvate: sugar phosphotransferase system (PTS)
  • prokaryotic cell feature
63
Q

Iron uptake

A
  • Micro organisms require iron
  • ferric iron is very insoluble so uptake is difficult
  • Micro organisms secrete siderophores to aid in uptake
  • siderophores complexes with ferric ion
  • complex is then transported into cell

Microbiology (5 decks)

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