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archea Flashcards

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1
Q

How are archaea broadly classified?

A

Into four superphyla

If the question says “broadest classification,” this is the answer.

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2
Q

What are the four archaeal superphyla?

A
  • Euryarchaeota
  • TACK
  • DPANN
  • Asgard

MEMORY TIP: E-T-D-A (Eat The Delicious Archaea)

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3
Q

Which archaeal superphylum is best studied and most diverse?

A

Euryarchaeota

EXAM TIP: Default archaea questions often point here.

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4
Q

What defines methanogens?

A
  • Produce methane (CH₄)
  • Strict anaerobes

EXAM TIP: Oxygen = toxic to methanogens.

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5
Q

Why are methanogens important ecologically?

A

They contribute to global methane production

WHY IT MATTERS: Methane = greenhouse gas.

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6
Q

Where are methanogens commonly found?

A
  • Wetlands
  • Sediments
  • Animal digestive tracts

MEMORY TIP: “Swamps and stomachs.”

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7
Q

Which methanogen is found in the human gut?

A

Methanobrevibacter smithii

EXAM TIP: This is the ONLY species name worth memorizing here.

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8
Q

Why might methanogens affect human health?

A

They influence gut microbial metabolism

EXAM TRAP: They are NOT pathogens.

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9
Q

What defines halophiles?

A

Require very high NaCl concentrations

EXAM TIP: Salt isn’t optional — it’s required.

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10
Q

How do halophiles prevent dehydration in salty environments?

A

Maintain high intracellular K⁺ concentrations

MEMORY TIP: K⁺ inside balances NaCl outside.

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11
Q

Why do halophiles have acidic proteins?

A

Acidic residues help proteins function in high salt

EXAM TIP: Protein adaptation is key.

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12
Q

Why do halophiles often have high GC content genomes?

A

Increased DNA stability

EXAM TIP: GC = stronger hydrogen bonding.

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13
Q

How do some halophiles obtain energy?

A

Utilize sunlight

EXAM TRAP: This is NOT photosynthesis like plants.

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14
Q

What temperature range defines thermophiles?

A

Elevated temperatures above normal mesophiles

EXAM TIP: Exact temperature numbers are usually not required.

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15
Q

Why are archaeal enzymes stable at high temperatures?

A
  • Protein structure adaptations
  • Membrane stability

WHY IT MATTERS: Industrial enzyme use.

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16
Q

What does TACK stand for?

A
  • Thaumarchaeota
  • Aigarchaeota
  • Crenarchaeota
  • Korarchaeota

EXAM TIP: You are NOT expected to list all adaptations for each.

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17
Q

What environments are Crenarchaeota associated with?

A
  • Thermophiles
  • Hyperthermophiles
  • Acidophiles
  • Barophiles

MEMORY TIP: “All the extremes.”

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18
Q

What makes Thaumarchaeota unique?

A
  • Mesophiles and psychrophiles
  • Important in biogeochemical cycling

EXAM TIP: This group breaks the “only extremophiles” myth.

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19
Q

How are Thaumarchaeota commonly detected?

A

rRNA sequence analysis

WHY IT MATTERS: Many are difficult to culture.

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20
Q

Why are Korarchaeota poorly understood?

A

They are uncultivated

EXAM TIP: “Uncultivated” often = limited data.

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21
Q

What defines DPANN archaea?

A
  • Extremely small cells
  • Reduced genomes
  • Metabolic dependence

MEMORY TIP: DPANN = “Depends.”

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22
Q

Which archaeon represents DPANN?

A

Nanoarchaeum equitans

EXAM TIP: Nano = very small.

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23
Q

What is the approximate size of Nanoarchaeum equitans?

A

~0.4 µm diameter

EXAM TIP: Smaller than most bacteria.

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24
Q

Why can’t DPANN archaea survive independently?

A

They rely on host organisms for metabolism

EXAM TRAP: They are NOT viruses.

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25
Why is the **Asgard superphylum** important?
It may represent the evolutionary link to eukaryotes ## Footnote EXAM TIP: If the question mentions “origin of eukaryotes,” think Asgard.
26
Which **Asgard archaeon** is commonly discussed?
Lokiarchaeota ## Footnote MEMORY TIP: Loki = trickster god → tricky evolutionary role.
27
Where were **Lokiarchaeota** discovered?
Near Loki’s Castle hydrothermal vents (Norway) ## Footnote EXAM TIP: Location questions show up more than you’d expect.
28
What genes make **Asgard archaea** special?
Genes encoding eukaryotic signature proteins ## Footnote WHY IT MATTERS: Supports eukaryotes evolving from archaea.
29
Archaea vs Bacteria: **membrane linkage type**
* Archaea: Ether * Bacteria: Ester ## Footnote EXAM TIP: This is one of the MOST tested distinctions.
30
Archaea vs Bacteria: **membrane lipids**
* Archaea: Isoprenoids * Bacteria: Fatty acids ## Footnote MEMORY TIP: Branched = archaea.
31
Archaea vs Bacteria: **cell wall composition**
* Archaea: Pseudomurein or S-layer * Bacteria: Peptidoglycan ## Footnote EXAM TRAP: Not all archaea even have pseudomurein.
32
Archaea vs Eukarya: **nucleus**
* Archaea: No nucleus * Eukarya: Nucleus present ## Footnote EXAM TIP: Histones ≠ nucleus.
33
Archaea vs Eukarya: **histones**
* Both have histones * Archaea use H3 and H4 ## Footnote EXAM TIP: This similarity is evolutionary evidence.
34
True or False: All archaea are **extremophiles**
False ## Footnote EXAM TIP: Many live in moderate environments.
35
True or False: Archaea are bacteria with unusual membranes
False ## Footnote EXAM TIP: Domain-level distinction.
36
True or False: Archaea lack **cytoskeletal elements**
False ## Footnote WHY IT MATTERS: Outdated idea.
37
True or False: Antibiotics that target peptidoglycan are effective against archaea
False ## Footnote EXAM TIP: Mechanism matters.
38
One sentence summary of **Archaea**
Prokaryotes with unique membranes and eukaryote-like genetic machinery ## Footnote MEMORY TIP: “Hybrid life form.”
39
If you see ether linkages + histones + no nucleus, what **domain** is it?
Archaea ## Footnote EXAM TIP: That combo is unbeatable.
40
What concept best explains why **archaea** matter evolutionarily?
They bridge bacteria and eukaryotes ## Footnote WHY IT MATTERS: Origin of complex life.
41
Why can’t habitat alone define **Archaea** as a domain?
Because Archaea are found in extreme and normal environments ## Footnote EXAM TIP: “Extremophile” ≠ defining feature.
42
What molecular evidence was most important in redefining domains of life?
Ribosomal RNA (rRNA) sequence comparisons ## Footnote WHY IT MATTERS: rRNA evolves slowly → good evolutionary marker.
43
Why was **rRNA** chosen instead of protein sequences?
* Present in all organisms * Conserved function * Slow evolutionary change ## Footnote EXAM TIP: Expect “why rRNA?” questions.
44
What did **Carl Woese**’s work fundamentally change?
The classification of life from 2 kingdoms to 3 domains ## Footnote MEMORY TIP: Woese = “blew up the tree of life.”
45
How does **LUCA** relate differently to bacteria, archaea, and eukarya?
* Bacteria diverged early * Archaea and eukarya share a more recent common ancestor ## Footnote EXAM TRAP: LUCA did NOT directly become archaea.
46
What evidence links **archaea** more closely to eukarya than bacteria?
* Histones * Transcription machinery similarities * rRNA sequences ## Footnote EXAM TIP: If histones are mentioned → think archaea/eukarya.
47
Why is archaeal size important for classification questions?
Their size overlaps with bacteria, not eukarya ## Footnote EXAM TIP: Size alone won’t distinguish bacteria vs archaea.
48
Which archaeal **morphologies** are most likely to appear on exams?
* Cocci * Bacilli * Irregular ## Footnote EXAM TIP: “Irregular” is often the correct archaea answer.
49
Why is archaeal DNA considered **prokaryotic**?
* Located in nucleoid * Circular chromosome * No membrane-bound nucleus ## Footnote EXAM TIP: No nucleus ≠ simple DNA packaging.
50
Why is archaeal DNA considered **eukaryotic-like**?
It is wrapped around histones ## Footnote KEY DETAIL: H3 and H4 histones specifically.
51
Why is the presence of **histones** in archaea surprising?
Histones were once thought to be exclusive to eukarya ## Footnote EXAM TIP: This is a classic “why archaea are unique” question.
52
How does archaeal DNA packaging compare to eukaryotic nucleosomes?
* Similar structure * Fewer histones * Simpler organization ## Footnote MEMORY TIP: “Proto-nucleosomes.”
53
Why was the discovery of an archaeal **cytoskeleton** important?
It challenged the idea that prokaryotes lack cytoskeletal structures ## Footnote EXAM TIP: “Prokaryotes have no cytoskeleton” is outdated.
54
What is **Ta0583**?
An archaeal protein homologous to eukaryotic actin ## Footnote MEMORY TIP: “TA” → Think “actin.”
55
Which bacterial protein do some archaeal cytoskeletal proteins resemble?
MreB ## Footnote EXAM TIP: MreB = shape maintenance.
56
What does cytoskeletal similarity suggest about **evolution**?
Shared ancestral cellular machinery ## Footnote WHY IT MATTERS: Supports evolutionary links.
57
What is the single most testable feature of archaeal **membranes**?
Ether linkages ## Footnote EXAM TIP: Ether = archaea, Ester = bacteria/eukarya.
58
Why are **ether linkages** advantageous in extreme environments?
They are more chemically stable than ester linkages ## Footnote MEMORY TIP: Ether = tougher bond.
59
What are **isoprenoids** and why are they important?
Branched lipid chains unique to archaea ## Footnote EXAM TIP: Branched ≠ fatty acids.
60
How do **monolayer membranes** benefit archaea?
Increased stability at high temperatures ## Footnote EXAM TRAP: Monolayers are NOT fragile.
61
Which archaea are most likely to have **monolayer membranes**?
* Thermophiles * Hyperthermophiles ## Footnote MEMORY TIP: One layer = less melting.
62
Why don’t many **antibiotics** work on archaea?
They lack peptidoglycan ## Footnote EXAM TIP: Penicillin targets peptidoglycan.
63
What replaces peptidoglycan in some archaeal **cell walls**?
Pseudomurein ## Footnote EXAM TIP: Similar function, different chemistry.
64
What sugar distinguishes **pseudomurein** from peptidoglycan?
N-acetyltalosaminuronic acid ## Footnote MEMORY TIP: If it’s hard to pronounce, it’s archaea.
65
Why is **pseudomurein** resistant to lysozyme?
Different glycosidic linkages ## Footnote EXAM TIP: Lysozyme ≠ effective on archaea.
66
Why is the **S-layer** important for archaea survival?
* Protection * Structural support * Adherence ## Footnote EXAM TIP: S-layer ≠ capsule.
67
What is unique about archaeal **flagella**?
* Same function as bacteria * Different protein structure ## Footnote EXAM TRAP: Function similarity hides structural difference.
68
What are **cannulae** and why are they unusual?
Structures that physically connect archaeal cells ## Footnote MEMORY TIP: “Cell networking cables.”
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