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MICR2208 > 4 - Prokaryotic structure and function 2 > Flashcards

4 - Prokaryotic structure and function 2 Flashcards

1
Q

What are the proteins contained in the periplasm involved in

A
  1. Nutrient acquisition
  2. Peptidoglycan biosynthesis
  3. Protein folding
    4.Contact dependent stress response systems
  4. Synthesis of pili and flagella
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2
Q

What two sugars make up cell walls (peptidoglycan)

A

Two alternating disaccharides:
- NAM (N-acetylmuramic acic)
- NAG (N-acetylglucosamine)

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3
Q

Stem peptide

A

Each glycan dimer is attached to a pentapepide (5 amino acids) this joins peptides

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4
Q

Glycan

A

Long strands of repeating sugar units

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5
Q

How is the NAG - NAM dimer connected

A

Beta - (1,4) - glycosidic bonds to form a long polymer

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6
Q

How are peptidoglycan strands linked

A

Crosslinked to each other by covalent bonds between the stem peptides. Can be direct (gram negative) or indirect (gram positive) using peptide inter bridge

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7
Q

Teichoic acid (+)

A

A polymer of glycerol or ribitol joined by phosphate groups. Unique to gram positive cell walls and negatively charged. Connected covalently to peptidoglycan and cytoplasmic membrane

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8
Q

Roles of teichoic acid

A
  1. Help maintain peptidoglycan structure,
  2. cell division
  3. protect against harmful substances (anti biotics)
  4. major inflammatory mediator
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9
Q

Bacteria outer membrane (-)

A

Unique to gram negative bacteria. Asymmetric bilayer. Contains Outer Membrane Proteins (OMPs)

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10
Q

Explain the asymmetric bilayer of the outer membrane

A
  • Inner leaflet phospholipids and proteins (Braun’s lipoprotein)
  • Outer leaflet 70% glycolipid (Lipopolysaccharides)
  • Negatively charged
  • Essential for life
  • Endotoxin - simplitates immune cells (lipid A portion)
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11
Q

Function of the outer membrane and outer membrane channels

A
  • Connect periplasm to environment
  • Porins (form channels)
  • Transport of nutrients
  • Secretion of proteins
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12
Q

Mycobacterial cell wall

A
  • Gram positive
  • Thin layer of peptidoglycan surrounded by mycolic acid layers.
  • Waxy, hydrophobic, high lipid content.
  • Function: permeability and fluidity. Allows to thrive air water interfaces
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13
Q

How are Mycobacterium stained

A

Ziehl-Neelsen or Kinyoun’s stain

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14
Q

Archaea plasma membrane

A
  • Composed of branched chain hydrocarbons attached to glycerol by ether links.
  • Can be monolayer (C40 tetraether lipid) or bilayer (C20 diether lipid)
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15
Q

Special characteristic of archaea monolayer plasma membrane

A

More rigid and resist extreme heat

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16
Q

Archaea cell wall

A

Many different types (no peptidoglycan present). Can stain positive or negative

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17
Q

Gram negative Archaea cell wall stain

A

1 or 2 S-layers (20-40 nm) above cell membrane
Interlocking protein units

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18
Q

Gram positive Archaea cell wall stain

A

Made up of Pseudomurein, Not sensitive to penicillin or lysozyme

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19
Q

Bacteria external structures

A
  • Capsules
  • Slime Layers
  • Sheaths and Prostheca
  • Pili / Fimbriae, Flagella
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20
Q

Roles of bacterial ecternal structures

A

Protection from the environment, Adhesion, Motility

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21
Q

Capsule

A

Organised matrix firmly anchored to cell

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22
Q

Slime layer

A

Diffuse, disorganised matrix, easily removed

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23
Q

composition of capsules and slime layers

A

Polysaccharides (majority) and Poly amino acid

24
Q

role of capsules and slime layers

A
  1. Resist phagocytosis, 2.Protection from desiccation,
  2. Adherence,
  3. Gliding motility (slime layer)
25
Q

Sheaths

A

Stiff polysaccharide tube containing cells.
Function: Attach to solid surfaces
Protection from protozoan predators
Sieve for acquiring nutrients

26
Q

Prosthecae

A

Extensions containing cell wall and plasma membrane.
Function: Attach to solid surfaces

27
Q

Pili/Fimbriae

A

Short, fine, hair-like appendages, Hollow brittle tube
Consisting of multiple pilin subunits organised as a helix

28
Q

how are types of pili defined

A

Types I-IV defined by Length, Diameter of the fibre and Location on the cell (Polar, Peritrichous, Single, multiple)

29
Q

Function of pili/fimbriae

A
  1. Adherence
  2. Twitching motility
  3. Gliding motility
30
Q

Sex pillus

A

Larger than other pili, transfer of DNA from host to recipient. Conferred by a conjugative plasmid (not encoded on host nucleoid)

31
Q

Role of sex pillus

A

Exchange of genetic content, spread of antibiotic resistance on R plasmids

32
Q

Flagella

A

Longer hair like appendage consisting of a hollow filament composed of flagellin protein, hook, basal body. Basal motor structure drives rotation of flagellum (act as propeller)

33
Q

Role of flagella

A

Swimming in aqueous environments and seeking nutrients (chemotaxis)

34
Q

What is chemotaxis (Tumbling)

A

The movement of cells or organisms in response to chemical gradients in their environment.

35
Q

Positive chemotaxis

A

Movement towards a higher concentration (attractant)

36
Q

Negative chemotaxis

A

Movement towards decreasing concentration (repellent)

37
Q

Name two alternate cell structures

A

Endospores and Conidiospores

38
Q

Endospores

A

Produced by a small number of bacteria (eg Bacillus), can be terminal (end), subterminal (just before end) or central (middle)

39
Q

Characteristics of endospores

A

Dormant, resist extreme conditions which would kill the vegetative cell (eg. starvation, heat, salt) and core contains dipicolinic acid

40
Q

Sporulation

A

Occurs in response to limited carbon, nitrogen, phosphorus. Endospore germination occurs in favourable conditions to become vegetative cell

41
Q

What are the steps of sporulation

A
  1. Asymmetrical cell division
  2. Engulfment of forespore
  3. Cortex and coat synthesis
  4. Endospore maturation, 5. Sporangium lysis
42
Q

Conidiospores

A

Produced by Streptomyces in response to nutrient starvation. Thin wall spores at the end of filaments. Resistant to desiccation but not heat.

43
Q

Periplasm

A

Located: Gram -tve
Space between the Outer membrane and the Inner membrane

44
Q

What are Sheaths made from

A

Ferric or Manganic Oxides

45
Q

Attachment locations of Flagella

A

Polar- protruding from one end
Peritrichous - protruding from uniform points across the bacterial surface
Mono- or multiple

46
Q

Axial filaments

A
  • Specialised flagella that are trapped inside the periplasm of gram negative cell walls
  • Arranged in a helical shape
47
Q

Axial filaments Function

A

Function for locomotion
– Corkscrew through liquid
– Crawl on surfaces

48
Q

Endospore Structure

A

Ribosomes
DNA
Core wall
Cortex
Spore coat
Exosporium

49
Q

Compare the archaeal cell wall to Gram positive and Gram negative
bacterial call walls.

A
50
Q

Describe the features of the cell wall of Mycobacteria and explain why this
organism is Gram positive.

A
51
Q

Compare the structure and functions of pili and flagella.

A
52
Q

What are capsules and slime layers and what functions do they perform?

A
53
Q

Describe endospore formation. What are the characteristics of endospores?

A
54
Q

Compare a Gram negative cell wall to Mycobacterial cell walls.

A
55
Q

List four features of an endospore and describe the sporulation cycle of
endospores using a diagram.

A

MICR2208 (26 decks)

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