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Medical Microbiology > Section 1- Prokaryotic Cell Structure/Function > Flashcards

Section 1- Prokaryotic Cell Structure/Function Flashcards

1
Q

3 domains of life

A 
Bacteria
Archaea
Eukarya
All contain single-celled microbes
Archaea and Eukarya more closely related
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2
Q

Prokaryotes

A

Lack nuclear membranes

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3
Q

Archaea

A

Prokaryote

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4
Q

Bacteria

A

Prokaryote
Range from 0.2 to 2 microns in diameter
Seen mostly by electron microscopy

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5
Q

Eukarya

A

Eukaryote
Have nuclear membranes
Ex: paramecium, fungi, plants, animal

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6
Q

Virus

A

Non living

Smaller than bacteria

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7
Q

Coccus, Cocci

A

Spherical cells

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8
Q

Bacillus, bacilli

A

Rod-shaped cells

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9
Q

Spiral-shaped bacteria

A

Usually motile
Comma-like
Coiled
Ex: spirochete

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10
Q

4 main types of Prokaryotic cells

A

Coccus
Coccobacillus
Bacillus
Vibrio

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11
Q

Pleomorphic bacteria

A

Can have many different appearances

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12
Q

Diplococci

A

Cocci pair

One plane of division

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13
Q

Streptococci

A

Cocci chain

One plane of division, repeated

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14
Q

Staphylococci

A

Cocci bunch

3 planes of division, repeated

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15
Q

Binary fission- multiplication

A

How bacteria divide
Cell replicates DNA, membrane elongates to separate DNA molecules, cross-wall forms and membrane invaginates, cross-wall forms completely, daughter cells separate

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16
Q

Endospores

A

Produced by gram (+) Bacillus and Clostridium species
Each vegetative cell transforms into one endospore
Each endospore germinates to form one vegetative cell
*Dormant state for bacteria
Constitute a defense strategy against hostile or unfavorable conditions
Very resistant to drying, heat, radiation, and disinfectants
Can remain viable for 10-1000 years
Serious concern to food industry and hospitals (1000 cases/day)
Potential biological weapons of mass destruction (b/c create toxins)

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17
Q

Endospore Formation steps

A

DNA replicates, membrane invaginates to form forespore, membrane engulfs forespore in 2nd membrane, and vegetative cell’s DNA disintegrates
Next, cortex of calcium and dipicolinic acid deposits between 2 membranes, spore coat forms around endospore, endospore “matures” (coat thicker), endospore released

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18
Q

Differential stains

A

Ex: Gram Stain

Acid-Fast Stain

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19
Q

Gram Stain

A

Gram (+) vs Gram (-)
Differentiates MOST bacteria
Steps: Crystal Violet, Gram’s Iodine (Fixes stain), Decolorizer (Alcohol or Acetone), Safranin

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20
Q

Gram (+)

A

Stain purple

Ex: Staphylococcus aureus

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21
Q

Gram (-)

A

Stain red/pink

Ex: Escherichia coli

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22
Q

Gram stain NOT used for

A

Atypical cell walls

  • Mycoplasmas
  • Archaea
  • Mycobacterial/Nocardia
23
Q

Mycoplasmas

A

Only bacteria without cell wall

Sterols in plasma membrane

24
Q

Archaea

A

Not bacteria

Wall-less or have walls of pseudomurein

25
Mycobacteria/ Nocardia
Acid fast bacteria (AFB) Very waxy outer layer--> resistant Ex: Mycobacterium tuberculosis, Mycobacterium leprae, Nocardia asteroides
26
Acid-Fast stain
AFB resist decolorization with acid-alcohol and stain raid, the color of the initial stain, CARBOL FUCHSIN Other bacteria will be decolorized and stain blue with counterstain, METHYLENE BLUE
27
Central endospores
Bacillus Endospore stain (green within red) Stain everything but spore
28
Terminal endospores
Clostridium botulinum and Clostridium tetani
29
Clostridium botulinum
Causes botulism Most potent toxin known Disease is an intoxication by neurotoxin Forms spores Clinical sign=flaccid paralysis (no muscles contract) Most affects infants less than 6 months b/c they are more susceptible to spores; HONEY often infected 150 cases/year
30
Clostridium tetani
Causes tetanus Neurotoxin; causes spastic paralysis (all muscles contract) Lockjaw first sign
31
External structure of prokaryotes
``` Flagellum (flagella) Fimbria (fimbriae) Pilus (pili) Capsule Glycocalyx ```
32
Flagellum
``` Not on every bacterium Molecular motor-responsible for movement Propels bacterium forward 3-12 microns long Whiplike structures that extend beyond surface of cell Made up of flagellin protein Rotate 360 degrees ```
33
Motile cells
Rotate flagella to run or tumble Ex: Helicobacter pylori Flagella proteins are H antigens
34
Fimbriae and Pili
``` Same function Nonmotile extensions Sticky, hairlike projections Used to adhere/attach May be 100s per cell Shorter than flagella Serve important function in biofilms Virulence determinants PILI ONLY- can join 2 bacterial cells and mediate transfer of DNA via conjugation- called conjugation pili or sex pili ```
35
Glycocalyx
``` "Slime" Loosely attached to cell surface Sugary, extracellular polysaccharide Protects cells from drying out Promotes adherence ```
36
Capsule
``` Firmly attached to cell surface Polysaccharide Protects cells from drying out Promotes adherence (adherence factor) Antiphagocytic (WBCs don't recognize) Virulence factor Antigens- stimulate immune response Vaccine component (if you inject purified capsule, body will may antibodies against it) ```
37
Planktonic bacteria
Free living bacteria
38
Biofilm
Community of bacteria surrounded by slime
39
Prokaryotic cell wall
Provides structure and shape and protects cell from osmotic forces Assists some cells in attaching to other cells or in eluding antimicrobial drugs Absent in animal cells Target of important antibiotics "-cillins" target cell wall
40
Bacterial cell wall
2 basic types: Gram+ and Gram- | Most have peptidoglycan
41
Peptidoglycan
Polysaccharide polymer of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) Has cross-linked tetrapeptides also that make it stronger In most bacterial cell walls NOT in Mycoplasma species Mesh-like coat around cell Function: shape, protection, diffusion (mesh) Target of antibiotics- ex: penicillin stops cross links
42
Gram (+) cell wall
``` Simple Thick peptidoglycan Stains purple Has teichoic acids (anchor peptidoglycan to cell membrane) One membrane (no outer membrane) No LPS ```
43
LPS
``` Lipopolysaccharide Endotoxin (toxin within cell) Made up of Lipid A (toxic), a core oligosaccharide, and the O polysaccharide antigen Lipid A is released from dead cells when the cell wall disintegrates; causes fever, vasodilation, inflammation, shock, and blood clotting; released when antimicrobial drugs kill bacteria ```
44
Gram (-) cell wall
``` Complex Thin peptidoglycan Stains red/pink No teichoic acids 2 membranes (Has outer membrane) LPS present Has periplasmic space between outer and cytoplasmic membranes ```
45
Protoplast
Gram (+) bacterium minus a cell wall Ex: formed when lysozyme destroys the cell wall Cell wall can be regrown
46
Spheroplast
Gram (-) bacterium minus cell wall
47
Outer membrane
``` Gram (-) only Protects from phagocytes and antibiotics Has LPS Porins form channels through membrane Has outer membrane proteins (OMPs) ```
48
Periplasmic space
Between outer membrane and cell membrane in gram (-) bacteria Contains peptidoglycan and periplasm with water, nutrients, digestive enzymes, and transport proteins
49
Internal structures of prokaryotes
Cytoplasmic membrane Cytoplasm Endospores Inclusions (not covered)
50
Prokaryotic cytoplasmic membrane
``` Phospholipid bilayer Function similar to eukaryotic membrane Electron transport chain Energy production (ATP) Transport proteins ```
51
Prokaryotic cytoplasm
Contains ribosomes (protein synthesis sites) Inclusions (reserve energy molecules) Cytoskeleton (cell shape) Plasmids Antibiotic targets (Nucleoid- 1 or 2 circular ds DNA, mRNA, 30S/50S ribosomal subunits)- all gene to protein targets
52
Plasmids
Usually circular Extrachromosomal DNA Confer antibiotic resistance
53
Ribosomes
Site of protein synthesis 30S+50S subunits 70S ribosomes

Medical Microbiology (5 decks)

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