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Bio 322 > Unit 4 - Lec 14 > Flashcards

Unit 4 - Lec 14 Flashcards

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Biology 101 flashcards
1
Q

when did LUCA appear?

A

4 bya

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2
Q

what is LUCA?

A

thermophilic

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3
Q

what are hyperthermophiles mostly?

A

mostly Archaea

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4
Q

what can bacteria also be?

A

hyperthermophilic

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5
Q

what is the superheated vent water?

A

sterile- no microogranisms
- no biochemical markers that signal life

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6
Q

who is the record holder for temp?

A

methanopyrus

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7
Q

what happens at 150C?

A
  • ATP degrades
  • life forms have to deal with heat liability of a molecule that is universally distributed in cells
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8
Q

how to maintain stabilitity of DNA/RNA and proteins at higher temps?

A
  • thermostable proteins
  • thermosomes
  • chaperonins
  • reverse DNA gyrase
  • RNA modification
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9
Q

thermosome function?

A
  • keeps other proteins properly folded and functional at high temps
  • maintains DNA
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10
Q

what happens after heat shock treatment?

A

sufficient to enable cells to keep growing and dividing

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11
Q

thermostable proteins

A
  • specific folding
  • not specific amino acids
  • alpha helical structure in thermostable proteins
  • very hydrophobic core - can’t easily fold
  • high ionic interactions on surface - can’t easily fold
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12
Q

chaperonins

A

heat shock proteins
- help refold partially denatured proteins

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13
Q

DNA/RNA involved thermostability

A
  • increased K+
  • reverse DNA gyrase
  • reverse gyrase introduces positive supercoils into DNA
  • pos supercoiling stabilizes DNA
  • highly basic DNA-binding proteins
  • heat resistant lipids
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14
Q

ribosomal RNAs

A
  • structural and functional components of ribosome- cell’s protein synthesizing apparatus
  • small ribosomal subunit in hyperthermophiles has 15% greater proportion of GC base pairs
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15
Q

what does higher GC content of ribosomal RNA confer?

A

greater thermal stability

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16
Q

GC content of genomic DNA of hyperthermophiles is often _____

A

low

17
Q

hypothesis for hyperthermophilic archaea, h2, microbial evolution

A
  • biological molecules, biochemical processes and first cells arose on Earth around hydrothermal springs and vents on sea floor
  • phylogeny of modern thermophiles suggests that they may be closest remaining descendants of ancient cells
18
Q

what does the oxidation of H2 link to?

A

reduction of Fe3+, S^0, NO3- and sometimes O2

19
Q

what is commonly spread in hyperthermophiles and why?

A

use of H2
H2 was available and there was many suitable inorganic e acceptors in primordial enviro
- metabolism evolved in primitive organisms

20
Q

where do chemolithotrophic organisms live?

A

hottest temp possible
- 110C

21
Q

what is the least heat-tolerant of all bioenergetic processes?

A

photosynthesis
- no hyperthermophilic representatives

22
Q

hydrogen-metabolizing bacteria

A

H2 is sole e donor
O2 is e acceptor
fix CO2
hydrogenase enzyme
microaerophilic
Ni2+ must be present
some fix N2

23
Q

what do diverse aerobic bacteria use?

A

atmospheric H2 for growth and survival

24
Q

H2 oxidation

A
  • globally significant process
  • regulates composition of atmosphere
  • enhances soil biodiversity
  • drives primary production in extreme enviro
25
Q

atmospheric H2 oxidation

A
  • uncharacterized members of Ni-Fe hydrogenase superfamily
26
Q

what conditions are unsuitable for enzymes?

A

very low level H2 and O2

27
Q

NiFe hydrogenase

A

membrane bound H2 oxidizing metalloenzymes
low affinity to H2
no support oxidation of atmospheric H2
O2 poisoning problem

28
Q

what are high affinity lineage NiFe hydrogenases?

A

capable to transfer electrons derived from atmospheric H2 oxidation to ETC

29
Q

what are newly discovered enzymes?

A

significantly higher affinity for H2 and are insensitive to inhibition by O2

30
Q

Ginter et al.

A

determined cryo-electron microscopy structure of hydrogenase Huc from Mycobacterium smegmatis

31
Q

Huc

A
  • enzyme that oxidizes atmospheric H2
  • O2 tolerant hydrogenase
  • multiple metal clusters
  • highly stable at room temp with melting temp 78.3C
  • oxidize atmospheric H2 below levels of detection in chromatography
  • gas channels provide entrance for H2 (road to active site)
32
Q

was O2-tolerant hydrogenase from E.coli Hyd1 able to tolerate high O2 levels?

A

no

33
Q

structural basis for energy extraction from H2

A

four-lead clover
associated with membrane vesicles via stalk-like protrusion
cellular membrane
activity mainly associated with soluble fraction

34
Q

where are bottlenecks?

A

between active site and enzyme surface
- H2 enters active site
- O2 excluded by bottlenecks
- O2 not getting close to active site

35
Q

what is the critical point in O2-insensitivity?

A

bottleneck after three gas tunnels that precedes active site

Bio 322 (11 decks)

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