02 Prokaryotes Flashcards

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1
Q

How old are prokaryotes?

A

~3.5 billion years old

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2
Q

How large are prokaryotes?

A

0.5-5.5 micrometers

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3
Q

What is the function of the prokaryotic cell wall?

A

Maintain cell shape, prevent bursting in hypotonic environments – but NOT hypertonic environments

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4
Q

What is peptidoglycan?

A

Polymer ONLY in domain bacteria. Polymer structure with sugars cross-linked by short polypeptides.
Makes up cell wall.

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5
Q

What do plants and fungi have instead of peptidoglycan?

A

plants - cellulose

fungi - chitin

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6
Q

What are the two prokaryotic stains?

A

1: crystal-violet – stains purple, retained by gram-positive bacteria
2: safranin – pink, retained by gram-negative bacteria

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7
Q

What is a gram-positive bacterium?

A
  • Cell wall with thick peptidoglycan
  • Vulnerable to antibiotics which inhibit peptidoglycan synthesis
  • Stained purple by crystal-violet stain
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8
Q

What is a gram-negative bacterium?

A
  • Cell wall has thin peptidoglycan
  • Much less vulnerable to antibiotics
  • Stained pink by safranin stain
  • Also produces lipopolysaccharide (LPS) – toxic, causes fever
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9
Q

What is a prokaryotic capsule / slime layer?

A
  • Provides defense against dehydration / phagocytosis
  • Consists of polysaccharides, proteins
  • Capsule = rigid, strong
  • Slime layer = looser protection
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10
Q

What is taxis?

A

Motility

Positive taxis = towards stimulus
Negative taxis = away from stimulus
Phototaxis = response to light
Chemotaxis = response to chemical

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11
Q

What are flagella?

A

Found in bacteria, eukaryotes, archaea BUT all developed independently => analogous traits

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12
Q

What are some differences between prokaryotic and eukaryotic flagella?

A
  • Prokaryotic one tenth size of eukaryotic
  • Prokaryotic not covered in plasma membrane
  • Composed of different proteins
  • Different propulsion methods
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13
Q

What are the constituent parts of the prokaryotic flagellum?

A
  • Motor rings embedded in cell wall / membrane
  • Hook
  • Filament – which rotates / propels cell
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14
Q

SEQ prokaryotic taxis

A

H+ ions pumped out of cell across plasma membrane by electron transport chain => forms chemiosmotic gradient

H+ diffuse back into cell through motor
=> hook turns
==> filament rotates
====> cell moves

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15
Q

Use E Coli in the human intestine as an example of how rapid reproduction can be an effective prokaryotic reproductive strategy despite small probabilities of individual gene mutation

A

probability of mutation = 1/10 million per gene per cell per division

c. 2^10 new cells produced in human intestine per day
= 2000 mutations of each individual gene per day
= ~9 million total mutations per day

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16
Q

Name three modes of prokaryotic genetic recombination

A

Transformation, transduction, conjugation

17
Q

What is genetic transformation?

A

Prokaryotic cell taking in foreign DNA from environment, e.g. in the Griffith experiment

18
Q

What is genetic transduction?

A

Either: phage transfers prokaryotic genes from one host to another

Or: viral replication – fragment of host DNA accidentally packaged into virus and injected into new host

19
Q

SEQ genetic conjugation in prokaryotes

A

Prokaryotic cells with F plasmid (F+ cells) = donor cells
F plasmid codes for production of pilis.

F+ uses pilis to attach to F- cell (recipient)
Pilis pull F- cell close to F+ cell
Mating bridge produced
One-way horizontal DNA transfer from donor to recipient

20
Q

Discuss prokaryotic metabolic diversity

A

Energy sources: photo, chemo

Carbon sources: inorganic (autotrophs); organic (heterotrophs)

Role of oxygen:
obligate aerobes - require for respiration
obligate anaerobes:
- either produce ATP without an electron transport chain (fermentation) OR use substance other than oxygen as final electron acceptor, e.g. nitrate, sulfate (= anaerobic respiration)
facultative aerobes - do both

21
Q

What does molecular evidence indicate regarding prokaryotic diversity?

A

Two domains: bacteria and archaea

  • Archaea closer to eukaryotes than prokaryotes are
  • strong evidence for horizontal gene transfer
22
Q

What are the primary groups in domain bacteria?

A

Proteobacteria

Chlamydia
- all parasites

Spirachetes
- lyme, syphillis

Cyanobacteria
- gram negative, photosynthetic, choloroplast precursors

Gram positive bacteria

23
Q

What are some examples of archaea?

A

Extremphiles - e.g. halophiles (salt), thermophiles

Methanogens - release methane