Question 1

Which of the following best explains why Archaeal membranes are more chemically stable than those of Bacteria and Eukarya?

Accepted Answer

Archaeal membranes contain ether linkages and branched isoprene chains.

Question 2

A patient presents with a bacterial infection. The bacteria are found to be resistant to lysozyme and penicillin. Which cell wall structure is most likely present?

Accepted Answer

Pseudomurein with β-1,3 glycosidic bonds

Question 3

Which component of the Gram-negative bacterial cell envelope is responsible for its toxicity in humans?

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 4

A Gram-positive bacterium is exposed to penicillin. What is the most likely effect on its cell wall?

Accepted Answer

Penicillin blocks the formation of peptide cross-links in peptidoglycan, weakening the cell wall.

Question 5

Which of the following structures is found in both Gram-positive and Gram-negative bacteria and is essential for selective permeability?

Accepted Answer

Cytoplasmic (cell) membrane

Question 6

A bacterium is observed to move toward a source of glucose. Which process is responsible for this directed movement?

Accepted Answer

Chemotaxis

Question 7

Which of the following best describes the structure of peptidoglycan in bacterial cell walls?

Accepted Answer

Alternating N-acetylglucosamine and N-acetylmuramic acid joined by $$\beta-1$$,4 linkages, with peptide cross-links.

Question 8

Which of the following is a function of bacterial capsules?

Accepted Answer

Assist in attachment to surfaces and prevent desiccation

Question 9

Which of the following statements about endospores is TRUE?

Accepted Answer

Endospores contain dipicolinic acid and small acid-soluble spore proteins (SASPs) that protect DNA.

Question 10

A researcher is studying a bacterium that forms biofilms and is highly resistant to phagocytosis. Which structure is most likely responsible for these properties?

Accepted Answer

Capsule

Question 11

Which of the following is a distinguishing feature of the cell envelope of Gram-negative bacteria compared to Gram-positive bacteria?

Accepted Answer

Presence of an outer membrane containing lipopolysaccharide (LPS)

Question 12

Which type of motility requires type IV pili and is powered by ATP hydrolysis?

Accepted Answer

Twitching

Question 13

Which of the following is NOT a function of the cytoplasmic membrane in bacteria?

Accepted Answer

Synthesis of peptidoglycan cross-links

Question 14

Which of the following best describes the arrangement of flagella in a peritrichous bacterium?

Accepted Answer

Flagella distributed over the entire cell surface

Question 15

Which of the following inclusions allows bacteria to orient and migrate along magnetic field lines?

Accepted Answer

Magnetosomes

Question 16

A bacterium is found to have a thick peptidoglycan layer, teichoic acids, and forms endospores. Which genus is most likely to possess these features?

Accepted Answer

Bacillus

Question 17

Which of the following is TRUE regarding the endosymbiotic origin of mitochondria and chloroplasts?

Accepted Answer

They contain circular DNA genomes and ribosomes similar to those of Bacteria.

Question 18

Which of the following is a major difference between the cell walls of Bacteria and Archaea?

Accepted Answer

Bacterial cell walls contain peptidoglycan, while most Archaeal cell walls contain S-layers or pseudomurein.

Question 19

Which of the following is a function of gas vesicles in cyanobacteria?

Accepted Answer

Confer buoyancy to optimize position for light exposure

Microbial Cell Structure and Function – Study Notes

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