Intro To Prokaryotes #2 Flashcards

from archaea onwards

You may prefer our related Brainscape-certified flashcards:
1
Q

what are the 3 broad groups of archaea?

A
  1. Methanogens (produce methane)
  2. Halophiles (salt loving)
  3. Thermophiles (heat loving)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how do archaeal cell envelopes differ from bacterial envelopes? (4)

A
  • s layer may be only component outside plasma membrane
  • some lack a cell wall
  • capsules & slime layers rare
  • lack peptidoglycan
  • s layer may be outside membrane separated by pseudomurein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what feature of the cell wall in archaea make them not susceptible to certain antibiotics (2)

A

no peptidoglycan so not susceptible to lysozyme, beta-lactam or glycopeptide antibiotics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are some key features of archaeal membranes? (5)

A
  • have distinct membrane lipids (diff from bacteria & euks)
  • branched chain hydrocs (alkyl isoprenoids) bonded to glycerol by ether bonds, not FAs linked by ester bonds
  • contain diglycerol tetraethers (not in bacteria or euks)
  • some have monolayer structure instead of bilayer (due to diglycerol ethers)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what evidence is there that archaea are in a distinct group and are not eukaryotes or bacteria ?

A

contain diglycerol tetraethers
have distinctive membrane lipids

(not in bacteria or euks)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how does pseudo murein differ from peptidoglycan (3)

A
  • contains L-aa rather than D-aa;
  • has β(1-3) glycosidic bonds and not β(1-4) glycosidic bonds
  • contains NAT & NAG not NAM & NAG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are archaeal chromosomes like?

A

similar to eubacteria, single closed DNA circle per cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what do archaeal ribosomes have in common with bacteria?

A

ribosomes are 70S but shape is variable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the protein synthesis of archaea sensitive and resistant to?

A
  • sensitive to anisomycin
  • resistant to chloramphenicol and kanamycin (like euks)

aniso affects archaea
chlorine and kites resistant to archaea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the EF-2 (elongation factor) in archaea sensitive to?

A

diphtheria toxin (like euks)

archaea elongates dippy (dipper)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

drugs

in what way is archaeal rna polymerase similar to that in eukaryotes?

A

insensitive to rifampicin and streptolydigin (usually inhibit bacterial transcription)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

drugs

what effect does streptolydigin have on prokaryotes?

A

bacteria: inhibit transcription
archaea: rna polymerase insensitive to streptolydigin

archaea like eukaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

drugs

what effect does rifampicin have on prokaryotes?

A

bacteria: inhibit transcription
archaea: rna polymerase insensitive to rifampicin

archaea like eukaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is the small subunit rrna in archaea similar to bacterial (1)

A

is 16S and similar in length to bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

which group was archaea more closely related to upon phylogenetic analysis?

A

eukaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what reasons are there to consider archaea prokaryotic ? (4)

A
  • similar cell sizes to bacteria
  • no nuclear membrane & cellular organelles
  • possess single, large, circular chromo
  • may have plasmids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is a protoplast ?

A

plasma membrane & everything within it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are plasmids? (2)

A
  • extrachromosomal DNA found in bacteria, archaea, some fungi
  • usually small, closed circular DNA molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are episomes ?

A

a type of plasmid that may integrate into chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is curing ?

A

the loss of a plasmid

21
Q

what is refractive index?

A

a measure of how greatly a substance slows the velocity of light

22
Q

focal point ? (F)

A

the specific place where lenses focus light rays at

23
Q

focal length (f) ?

A

the distance between centre of lens & focal point

24
Q

what does a short focal length mean?

A

more magnification

25
Q

what does a bright-field microscope do?

A

produces a dark image against a brighter background

26
Q

what is resolution ?

A

ability of a lens to separate (distinguish) small objects that are close together

27
Q

what is the relationship between wavelength of light and resolution?

A

shorter wavelength → greater resolution

28
Q

what is the numerical aperture ?

A

ability of the lens to gather light (n sin θ)

29
Q

what two factors is numerical aperture determined by?

A
  1. refractive index of the medium
  2. theta (1/2 the angle of the cone of light entering the objective lens)
30
Q

can any lens working in air have a numerical aperture greater than 1.0 ?

A

no, because air has a refractive index of 1.0

31
Q

how to increase numerical aperture in air ?

A

increase n by changing the medium in which the objective lens works from air to immersion oil

32
Q

what is the working distance ?

A

the distance between the front surface of lens & the surface of cover glass or specimen when it’s in sharp focus

33
Q

what is heat fixation ?

A

routine use with bacteria & archaea
preserves overall morphology but not internal structures

34
Q

what is chemical fixation ?

A

used with larger, more delicate organisms
protects fine cellular substructure & morphology

35
Q

what are chromophore groups ?

A

chemical groups with conjugated double bonds and gives dye its colour

36
Q

what is differential staining used for ?

A

to detect presence or absence of structures (e.g. gram staining)

37
Q

what causes the colour change in gram staining?

A

shrinkage of pores of thick peptidoglycan layer of gram-positive cells prevents loss of crystal violet during decolourisation step

38
Q

what is the terminus ?

A

site at which replication is terminated

located opposite of origin

39
Q

what is the replisome ?

A

group of proteins needed for DNA synthesis

40
Q

what is the growth curve?

A
  • observed when microorgs are cultivated in batch culture (in closed vessel w single batch of medium),
  • plotted as log of cell nr vs time
41
Q

what are the four distinct phases of the growth curve ?

A
  1. lag
  2. exponential
  3. stationary
  4. death
42
Q

explain the lag phase in the growth curve (2)

A

during this phase, cells are synthesising new components to replenish spent materials and adapt to the new medium

43
Q

describe the exponential phase in the growth curve (3)

A
  • rate of growth & division is constant & maximal,
  • cell pop is most uniform in terms of chemical & physical properties during this phase,
  • cells exhibit balanced growth

(aka log phase)

44
Q

what is balanced growth ?

A

cellular constituents are manufactured at constant rates relative to each other

45
Q

under what conditions does unbalanced growth occur?

A
  • change in nutrient levels
    shift up = poor to rich medium
    shift down = rich to poor medium
  • change in env conditions
46
Q

describe the stationary phase in the growth curve (3)

A
  • pop growth eventually ceases & total nr of viable cells remains constant
  • active cells stop reproducing or reproductive rate is balanced by cell death rate
47
Q

what are possible reasons for the stationary phase ? (4)

A
  • nutrient limitation
  • limited oxygen availability
  • toxic waste accumulation
  • critical pop density reached
48
Q

what are the two alternative hypotheses for the senescence and death phase in the growth curve ?

A
  1. cells are temporarily unable to grow (viable but not culturable VBNC) = cells are alive but dormant, capable of new growth when conditions are right
  2. programmed cell death (fraction of the pop genetically programmed to die i.e. commit suicide)