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D&D Unit 3 > Bacteria Structure and Function (complete) > Flashcards

Bacteria Structure and Function (complete) Flashcards

1
Q

Describe the rigid cell wall of bacteria. What are the functions?

A
  • External to cytoplasmic membrane that contain peptidoglycan
  • G(+) and G(-) have different cell wall structures

Functions:

1) Resists osmotic lysis
2) Maintains cell shape

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2
Q

Describe the peptidoglycan layer of bacteria

A
  • Forms rigid mesh surrounding cytoplasm
  • Consists of polymer of repeating units (GlcNAc and MurNAc)
  • these are crosslinked!
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3
Q

How does lysozyme interact with bacteria when inside the body?

A
  • Hydrolyzes peptidoglycan by cleaving glycosidic bond between MurNAc and GlcNAc
  • contributes to innate immune system
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4
Q

Describe the peptidoglycan layer in gram negative bacteria

A
  • THIN!

- Sparsely cross-linked

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5
Q

Describe the peptidoglycan layer of gram positive bacteria

A
  • THICK!
  • Extensively cross-linked
  • Also contains teichoic acids
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6
Q

Describe the outer membrane of gram negative bacteria. What are the functions?

A
  • A lipid bilayer
  • Contains lipopolysaccharide, lipoproteins, and porins

Functions:

1) Barrier to antibiotics
2) Protects against detergents and toxic compounds

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7
Q

Lipoproteins in the outer membrane of gram negative bacteria are covalently linked to what?

A

Peptidoglycans

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8
Q

What is the function of porins in the outer membrane of gram negative bacteria?

A
  • Form transmembrane channels

- Allow diffusion of hydrophilic molecules across membrane

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9
Q

Describe the outer membrane of gram positive bacteria

A
  • Have two layers or leaflets
  • Outer leaflet: LPS, Lipid A, core polysaccharide, O side chain
  • Inner leaflet: phospholipids
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10
Q

Describe teichoic acids.

A
  • A repeating polyglycerol-P or polyribitol-P backbone
  • Covalently attached to peptidoglycan layer
  • Help anchor the cell wall to membrane
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11
Q

Describe capsules

A
  • Loose, gelatinous outer surface layers
  • Consist of complex polysaccharides
  • Enhance virulence b/c it can resist phagocytosis of humans
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12
Q

Describe flagella

A
  • Appendages used for motility
  • Some bacteria have flagella all over surface (peritrichous)
  • some have just one (polar)
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13
Q

Describe pili (fimbraie)

A
  • Long, slender, proteinaceous, antigenic hair-like structures
  • Play role in adherance to surfaces and tissues
  • Abs against pili may block adherance

Also used for bacterial sexy time (aka transfer of chromosomes btwn bacteria)

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14
Q

Describe the cytoplasmic membrane

A
  • Barrier between the inside and outside of bacterial cell
  • Lipid bilayer made of phoslipids, proteins

Functions:

1) selective permeability
2) e(-) transport system

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15
Q

Describe the cytoplasm

A
  • Consists of aqueous solution of proteins and metabolites
  • Where metabolic processes occur

Include:

1) Ribosomes
2) Nucleoid

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16
Q

Describe ribosomes in bacteria

A
  • Where protein synthesis occurs

- Polyribosomes form when several ribosomes come together to interact with a single mRNA

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17
Q

Describe the nucleoid in bacteria

A
  • A specific area of the cytoplasm
  • Where DNA is located — tightly packed, coiled
  • No nuclear membrane surrounding the nucleoid
18
Q

Describe the bacterial chromosome

A
  • a single, double stranded CIRCULAR DNA molecule
19
Q

Describe plasmids

A
  • Extra-chromosomal, self-replicating DNA molecules
  • Not essential for bacterial viability

One type of plasmid called R factors:
- carry genes that determine resistance to antibiotics (Rrrrrr is for Rrrrrresitance!!!)

20
Q

Describe bacteriophages

A

Viruses that infect bacteria

  • inject DNA in bacterial cell
  • Viral DNA fuses w/ bacterial DNA
  • More viral proteins produced —> more viruses
21
Q

Explain the importance of different cell wall structures in bacteria

A

Bacterial shape determined by intracellular cytoskeletal elements and rigid cell wall

  • Structure determines function
22
Q

Describe a typical bacterial growth curve.

A
  • Bacteria are placed in a new environment and growth is measured
  • Divided into 3-4 phases (lag, exponential, stationary, death)

y-axis: log bacterial #
x-axis: time

23
Q

Explain the characteristics of lag phase

A

THINK: Adjustment phase

  • Produces new enzymes to new environment!
  • Establishes proper intracellular environment for optimal growth in this here new place
24
Q

Explain the characteristics of exponential phase

A

THINK: growth phase

  • rate of increase in cell #/mass is proportional to cell #/mass already present
  • constant interval required to double #/mass (GENERATION TIME)
25
Q

Explain the characteristics of stationary phase

A

THINK: plateau phase

  • Essential nutrients consumed; toxic metabs accumulate
  • Growth slows/ceases
  • Where most bacteria spend their time
26
Q

Explain the characteristics of death phase

A

THINK: death phase of course

  • Doesn’t always happen, but some bacteria can’t withstand stationary phase
  • there’s a decrease in total #/mass
  • Only seen when bacteria lyse!!! (makes sense, eh?)
27
Q

What are the different classifications for bacteria according to nutrition requirements?

A

1) Aerobe
2) Anaerobe
3) Indifferent
4) Facultative
5) Microaerophilic

28
Q

Describe aerobe bacteria’s nutritional requirements for growth response

A

GR: aerobic conditions

  • Requires O2
  • Cannot ferment
29
Q

Describe anaerobe bacteria’s nutritional requirements for growth response

A

GR: anaerobic conditions

  • Killed by O2
  • Fermentative metabolism
30
Q

Describe indifferent bacteria’s nutritional requirements for growth response

A

GR: aerobic and anaerobic

  • Ferments in presence or absence of O2
31
Q

Describe facultative bacteria’s nutritional requirements for growth response

A

GR: aerobic and anaerobic

  • Respires w/ O2
  • Ferments in absence of O2
32
Q

Describe microaerophilic bacteria’s nutritional requirements for growth response

A

GR: anaerobic (primary) and aerobic (small amount of growth)

  • Grows best at low [O2]
  • can grow w/o O2
33
Q

Define respiration

A
  • When O2 is used as the final e(-) acceptor in the electron transport/ATP generation process
  • Anaerobic resp: some bacteria may use inorganic substrates (nitrate, nitrite) as e(-) acceptors (not O2)
34
Q

Define fermentation

A
  • Organic compounds serve as both e(-) donors and acceptors

- No net oxidation/reduction between substrates and products

35
Q

Explain how metabolic “energy currency” is generated

A

Two types of currency:

1) ATP
2) Electrochemical gradients (proton motive force)

  • Generated by fermentation/respiration
  • Bacteria also need “reducing power” (NADPH, NADH)
36
Q

Explain why unique bacterial components are important as potential targets for antimicrobial therapy

A
  • Ensures you kill less of the host

- Selective inhibition of microbial growth at [drug] tolerated by host (aka SELECTIVE TOXICITY)

37
Q

What are the major groups of antibiotics used for human medicine?

A

1) Cell wall-active antimicrobials
2) Outer/cytoplasmic membrane-active antimicrobials
3) Protein synthesis inhibitors at ribosomal level
4) Nucleic acid synthesis inhibitors
5) Metabolic inhibitory antimicrobials

38
Q

What are the principal targets for cell wall-active antimicrobials?

A

Peptidoglycan

Examples

1) Beta-lactams
2) Vancomycin
3) Cycloserine

39
Q

What are the principal targets for outer/cytoplasmic membrane-active antimicrobials?

A
  • Outer and cytoplasmic membranes (duh)

- Use polymyxins to disrupt the membranes — they are cationic surfactants

40
Q

What are the principal targets for protein synthesis inhibitors at ribosomal level?

A

Bacterial ribosomes (b/c they are different from mammalian ribos!!!)

Examples:

1) Aminoglycosides
2) Tetracyclines
3) Chloramphenicol
4) Macrolides

41
Q

What are the principal targets for nucleic acid synthesis inhibitors?

A

Nucleic acid synthesis … :P

Examples:

1) Quinolones
2) Rifampicin

42
Q

What are the principal targets for metabolic inhibitory antimicrobials?

A

Specific metabolic reactions

Examples:

1) Sulfonamides (folic acid formation)
2) Trimethoprim (folic acid metabolism)
3) Isoniazid (lipid synthesis)
4) Metronidazole (anaerobic metabolism)

D&D Unit 3 (12 decks)

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