Question 1

Which of the following statements best explains why the 16S rRNA gene is used to construct the modern phylogenetic tree of life?

Accepted Answer

Because it is highly conserved across all domains of life, allowing for evolutionary comparisons.

Question 2

Which of the following is a unique feature of archaeal cell membranes compared to bacterial cell membranes?

Accepted Answer

Presence of ether-linked phospholipids with branched phytanyl sidechains.

Question 3

A microbiologist isolates a microorganism from a hot spring with a cell wall lacking peptidoglycan, ether-linked membrane lipids, and a 70S ribosome. Which domain does this organism most likely belong to?

Accepted Answer

Archaea

Question 4

Methanogens are a group of archaea that play a significant role in which of the following processes?

Accepted Answer

Production of methane from carbon dioxide and hydrogen in anaerobic environments

Question 5

Which of the following structures is unique to some archaea and is involved in surface attachment?

Accepted Answer

Hamus

Question 6

A student observes a microorganism with a square, cuboidal shape under the microscope. Which genus is most likely being observed?

Accepted Answer

Haloquadratum

Question 7

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

Accepted Answer

They contain a variety of specialized polysaccharides and proteins, but no peptidoglycan.

Question 8

Which of the following best describes the ribosomes found in archaea?

Accepted Answer

They are 70S ribosomes, but with some proteins more similar to eukaryotes than bacteria.

Question 9

Which of the following is FALSE regarding archaea?

Accepted Answer

Some archaea are known to cause diseases in animals and plants.

Question 10

Which of the following best explains why archaeal membrane lipids are more stable at high temperatures and high salt concentrations?

Accepted Answer

They contain branched phytanyl sidechains and ether linkages.

Question 11

A culture tube contains a microorganism that grows only at the bottom of the tube, away from oxygen. Which type of archaeal metabolism is most likely present?

Accepted Answer

Obligate anaerobe (methanogen)

Question 12

Which of the following is a defining functional characteristic that distinguishes methanogens from other archaea?

Accepted Answer

They are strict anaerobes that produce methane as a metabolic byproduct.

Question 13

Which of the following is NOT a difference between archaea and bacteria?

Accepted Answer

Archaea have 80S ribosomes, while bacteria have 70S ribosomes.

Question 14

Which of the following best describes the genetic material of most archaeal cells?

Accepted Answer

Single, circular chromosome.

Question 15

Which of the following external structures is found in both archaea and bacteria, but is composed of different proteins in each domain?

Accepted Answer

Flagella

Question 16

Which of the following is a correct association of organism and ribosome type?

Accepted Answer

Methanosarcina – 70S ribosome

Question 17

Which of the following best explains why archaea are not known to cause disease in humans?

Accepted Answer

Their metabolic pathways and cell structures are not compatible with pathogenicity in humans.

Question 18

Which of the following is a function of the archaeal glycocalyx?

Accepted Answer

Formation of biofilms and adherence to surfaces

Question 19

Which of the following best describes the evolutionary relationship between archaea, bacteria, and eukaryotes as revealed by 16S rRNA analysis?

Accepted Answer

Archaea are more closely related to eukaryotes than to bacteria.

lec 14

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