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Micro > lecture 4 - prokaryotic cell structure > Flashcards

lecture 4 - prokaryotic cell structure Flashcards

1
Q

cell

A

fundamental unit of life

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2
Q

cell characteristics

A
  • spherical or cylindrical
  • cytoplasmic membrane
  • chromosomes (DNA)
  • ribosomes for protein synthesis
  • reproduce to form progeny cells
  • obtain energy from environment
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3
Q

Bacterial cell structures

A

all: cell membrane, cytoplasm, ribosomes, chromosomes
most: cell wall, surface coating (glycocalyx)
some: flagella, pili, fimbriae, capsules, slime layers, endospores

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4
Q

what is the cytoplasm

A

Gelatinous solution (proteins)
Site for many metabolic activities
70%-80% water
Also contains large cell masses (ex: chromatin, ribosomes, granules)

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5
Q

how do chromosomes fit into cell

A

lots of DNA is packed into cell, some are “lysed” to let DNA escape out of cell so it isn’t so cramped
-it is compacted by twisting (supercoiling) and protein binding

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6
Q

characteristics of bacterial chromosomes

A

-single circular DNA strand located in the nucleotide (dense area of cell)

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7
Q

what s the cell envelope?

A

combination of cell membrane and wall

  • protects cell and contains cytoplasm
  • site of metabolic processes
  • gram - bacteria have two
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8
Q

what are the functions of the cell membrane

A
  • Energy reactions (ATP synthesis; proton and ion gradients)
  • Regulates transport (selectively permeable membrane)
  • Secretion
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9
Q

gram + bacteria structure

A

2layers
Cell membrane
Thick cell wall (peptidoglycan)

-Cell wall anchored to membrane and covered with sugar on the outside used to repelle water, and things you don’t want, helps with infection

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10
Q

Gram - bacteria structure

A

3 layers

  1. outter membrane
    - -Long sugar filaments extend from outside (lipopolysaccharides)
    - inside is phospholipid layer which is anchored to peptidoglycan layer by lipoproteins
    - has porin proteins for access into cell
    - only small molecules to penetrate
    - extra layer of protection that substances have to get through
  2. Thin cell wall (peptidoglycan)
  3. Cell membrane
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11
Q

characteristics of lipopolysaccharides

A

-located on Outer layer of the outer membrane

Three domains:

  • Lipid A (endotoxin - signals infection)
  • Core polysaccharide
  • O Antigen
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12
Q

what is the significants of the o antigen of lipopolysaccharides?

A

O antigen is the dominant antigen of Gram negative cells

V. cholerae O139
Caused epidemic in india in 90’s

O1 pandemic strain
E. coli O157

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13
Q

what does the cell wall do?

A

determines shape, provides structural support
-made of 1 cell peptidoglycan = sugar (glycan) and protein (peptide)

-when antibiotics target this cells pop because no structure or support - “lysis”

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14
Q

what is a flagellum?

A
  • propeller for swimming
  • driven by proton motive force
  • +/- chemotaxis and phototaxis
  • rotates rapidly
  • three parts: Filament (tail), hook (where it attaches), and basal body (motor)
  • vary in number and arrangement
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15
Q

how do bacteria move?

A

Flagellum can only propel when rotating counterclockwise
Tumbles (stops)
Runs (moves)

Speed:
Spin rate
Spin duration

“steering” is accomplished by running more than tumbling when it gets close to attraction

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16
Q

fimbriae

A

used for attachment

  • allow to stick to things
  • smaller than flagellum - short pills
  • can be 1000/ cell

-stick to one another to form bridge in HGT conjugation

17
Q

pili

A

used for:

  • attachment
  • genetic exchange (plasmids)
  • Motility (slow spiderman webgrab/ swing)
  • Very important for infection and interactions with host
18
Q

glycocalyx slime layer

A

a loose shield that protects some bacteria from loss of water and nutrients

19
Q

glycocalyx capsule

A

when the glycocalyx is bound more tightly to the cell and is denser and thicker

Ex) staphoccocus psnmonia has capsule to invade

20
Q

in general what types of bacteria usually have glycocalyx and why?

A
  • pathogenic bacteria
  • Capsule protects bacteria against phagocytosis by immune cells

-slimyness can determine pathogenicity

21
Q

virulence

A

Ability of a microbe to cause disease in another organism

22
Q

virulence factor

A

Microbial components that contribute to the ability to cause disease in a susceptible host

  • what is virulence factor for one organism may be a colonization factor for another (good vs bad bacteria)
    example: fili, fimbriae, capsules, flagella are used by commensals and pathogens
23
Q

how do bacteria survive in hosts

A

-Blocked phagocytic response: Bacteria escape and persist ***CAPSULES
Immune system can subsequently overreact when body can’t clear the bacteria

24
Q

how do microbes get into host cells?

A

Exoenzymes: break down and inflict damage on tissues OR dissolve host defence barriers

Examples
Mucinase
Keratinase
Collagenase
Hyaluronidase
25
Q

toxigenicity

A

ability to produce toxins

-weaken host, damage tissue

26
Q

toxinoses

A

a variety of diseases caused by toxigenicity

27
Q

toxemias

A

toxinoses in which the toxin is spread by the blood from the site of infection (ex: tetanus and diphtheria)

28
Q

intoxications

A

toxinoses caused by ingestion of toxins (botulism)

  • Not infected
  • Toxins can be very species specific in target
29
Q

what is the difference between exotoxins and endotoxins?

A

Eco - excreted by bacterium, target organs are damaged

endo: accidental ;not produced by bacteria. LPS (gram -)

30
Q

how do antimicrobials work?

A
  • drugs Disrupt the cell processes or structures of bacteria, fungi, and protozoa / stop viral replication
    -interfere with the function of enzymes required to synthesize and assemble macromolecules
    or, destroy structures already formed in the cell
31
Q

selectively toxic

A

GOAL

drugs kill or inhibit microbial cells without damaging host tissues

32
Q

where do antibiotics come from?

A

metabolic product of aerobic bacteria and fungi

-chemists alter structure of natural antibiotics to form new antibiotics

33
Q

how do antibiotics target cells?

A 
cell wall inhibitors
cell membrane inhibitors
metabolic inhibitors
DNA replication inhibitors
RNA Polymerase inhibitors
protein synthesis inhibitors
34
Q

minimum inhibitory concentration (MIC)

A

The lowest concentration of antibiotic at which a species can’t grow
-when antibiotics are used at incorrect MIC levels that bacteria isn’t killed results in evolution of resistance

Micro (12 decks)

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