Question 1

Which of the following features distinguishes archaeal cell membranes from those of bacteria and eukaryotes?

Accepted Answer

Presence of ether-linked lipids

Question 2

A researcher isolates a microorganism from a hydrothermal vent that thrives at 110 °C and has a lipid monolayer membrane. Which adaptation most likely contributes to its survival at such high temperatures?

Accepted Answer

Presence of branched isoprenoid chains in membrane lipids

Question 3

Which enzyme is unique to hyperthermophilic archaea and helps stabilize their DNA at high temperatures?

Accepted Answer

Reverse gyrase

Question 4

Methanobrevibacter smithii improves digestive efficiency in humans primarily by:

Accepted Answer

Removing hydrogen produced by bacterial fermentation

Question 5

Which feature most strongly supports the conclusion that archaea are evolutionarily closer to eukaryotes than to bacteria?

Accepted Answer

Use of histone proteins in DNA packaging

Question 6

The primary adaptive advantage of ether-linked lipids in archaeal membranes is that they:

Accepted Answer

Resist chemical hydrolysis and thermal degradation

Question 7

Hyperthermophilic archaea often possess lipid monolayers rather than bilayers. This adaptation primarily prevents:

Accepted Answer

Loss of membrane integrity at high temperatures

Question 8

Which group of archaea is most closely related to eukaryotes based on genetic analysis?

Accepted Answer

Asgard archaea

Question 9

Why are archaeal enzymes particularly valuable in lactose-free milk production?

Accepted Answer

They remain active at pasteurization temperatures

Question 10

Using archaeal β-galactosidase during pasteurization improves food safety because:

Accepted Answer

High temperatures suppress contaminating microbes

Question 11

Which of the following best explains why no archaeal pathogens have been identified in humans?

Accepted Answer

Archaea do not possess known virulence factors required for pathogenesis

Question 12

A patient with chronic constipation is found to have high levels of methane in their breath. Which archaeal species is most likely elevated in their gut?

Accepted Answer

Methanobrevibacter smithii

Question 13

Which adaptation allows archaeal proteins to remain stable and functional at extremely high temperatures?

Accepted Answer

Dense hydrophobic core and salt bridges

Question 14

Which archaeal group is characterized by extremely small cell and genome size, often requiring a symbiotic lifestyle?

Accepted Answer

DPANN group

Question 15

Which of the following is a major ecological role of Thaumarchaeota?

Accepted Answer

Nitrogen cycling in oceans and soils

Question 16

Which of the following best describes the function of the thermosome in hyperthermophilic archaea?

Accepted Answer

It refolds denatured proteins to restore their function

Question 17

Which of the following statements about archaeal cell walls is correct?

Accepted Answer

They may contain pseudopeptidoglycan or other unique polymers

Question 18

Which of the following best explains why archaeal β-galactosidase can hydrolyze lactose during milk pasteurization?

Accepted Answer

It is thermostable and remains active at 65 °C

Question 19

Which of the following is a defining characteristic of methanogens?

Accepted Answer

They produce methane as a metabolic byproduct

Question 20

Which of the following best describes the role of histone proteins in archaea?

Accepted Answer

They package DNA into compact structures, increasing thermal stability

lec 08:Archaea: Structure, Adaptations, Diversity, and Applications

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