Question 1

Which of the following statements best describes the main function of the cytoplasmic membrane in bacteria?

Accepted Answer

It acts as a selective permeability barrier, controlling the movement of substances into and out of the cell.

Question 2

Which feature distinguishes archaeal cytoplasmic membranes from bacterial cytoplasmic membranes?

Accepted Answer

Ether linkages between glycerol and isoprenoid chains.

Question 3

A bacterium is found to accumulate glucose against its concentration gradient using a system that chemically modifies glucose during transport. Which transport mechanism is being used?

Accepted Answer

Group translocation

Question 4

Which component of the Gram-negative bacterial cell envelope is responsible for its toxicity and acts as an endotoxin?

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 5

Which of the following best explains why lysozyme is effective against most bacteria but not against archaeal cell walls?

Accepted Answer

Archaeal cell walls lack peptidoglycan and instead may contain pseudomurein, which is not cleaved by lysozyme.

Question 6

A scientist observes a bacterium with a thick, tightly attached polysaccharide layer that is visible after India ink staining. What is this structure called and what is one of its main functions?

Accepted Answer

Capsule; assists in attachment to surfaces and protects against desiccation

Question 7

Which of the following is a function of small acid-soluble spore proteins (SASPs) found in bacterial endospores?

Accepted Answer

They bind and protect DNA from damage due to heat, UV, and desiccation.

Question 8

Which of the following best describes the movement of a peritrichously flagellated bacterium in the presence of a chemical attractant?

Accepted Answer

It alternates between runs and tumbles, but runs become longer in the direction of the attractant.

Question 9

Which of the following cell envelope structures is most likely to be found as the outermost layer in many Archaea and provides protection and shape?

Accepted Answer

S-layer

Question 10

A bacterium is observed to contain magnetosomes. What is the primary function of these structures?

Accepted Answer

To orient the cell within the Earth's magnetic field for optimal positioning.

Question 11

Which of the following best describes the energy source used by bacterial flagella for rotation?

Accepted Answer

Proton motive force

Question 12

Which of the following is a distinguishing feature of group translocation compared to simple transport and ABC transporters?

Accepted Answer

The transported substance is chemically modified during passage across the membrane.

Question 13

Which of the following statements about the Gram-positive bacterial cell wall is correct?

Accepted Answer

It contains a thick layer of peptidoglycan and teichoic acids.

Question 14

Which of the following best explains why Mycoplasma species are resistant to antibiotics that target cell wall synthesis?

Accepted Answer

They lack a cell wall and instead have a tough cytoplasmic membrane containing sterols.

Question 15

Which of the following is a correct sequence of events during endospore formation in Bacillus subtilis?

Accepted Answer

Asymmetric cell division, forespore engulfment, cortex and coat formation

Question 16

Which of the following best describes the function of porins in the outer membrane of Gram-negative bacteria?

Accepted Answer

They form channels that allow the passive diffusion of small molecules across the outer membrane.

Question 17

A bacterium is observed to move by extending and retracting pili from one cell pole, pulling itself forward. Which type of motility is this and what energy source does it use?

Accepted Answer

Twitching motility; ATP hydrolysis

Question 18

Which of the following best describes the role of teichoic acids in Gram-positive bacteria?

Accepted Answer

They are acidic molecules embedded in the cell wall, contributing to cell wall stability and ion transport.

Question 19

Which of the following is a correct description of the ABC transporter system?

Accepted Answer

It consists of a substrate-binding protein, a transmembrane transporter, and an ATP-hydrolyzing protein.

Question 20

Which of the following is a function of gas vesicles in aquatic bacteria?

Accepted Answer

They confer buoyancy, allowing cells to position themselves optimally in the water column.

Microbial Cell Structure and Function: The Cell Envelope, Surface Structures, and Motility

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