Question 1

Which of the following best describes the main function of the cytoplasmic membrane in bacterial cells?

Accepted Answer

It acts as a selective permeability barrier, allowing nutrients in and waste out.

Question 2

Which structural feature distinguishes archaeal cytoplasmic membranes from those of bacteria and eukaryotes?

Accepted Answer

Presence of isoprene chains and ether linkages in phospholipids

Question 3

A scientist isolates a cell with a thick peptidoglycan layer, teichoic acids, and no outer membrane. Which type of cell envelope does this cell most likely possess?

Accepted Answer

Gram-positive bacterial cell envelope

Question 4

Which of the following statements about the proton motive force is correct?

Accepted Answer

It is generated by the movement of protons across the cytoplasmic membrane.

Question 5

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

Accepted Answer

Lipid A portion of lipopolysaccharide (LPS)

Question 6

A patient is infected with a bacterium that is resistant to lysozyme and penicillin. The cell wall is found to contain pseudomurein. Which group does this organism most likely belong to?

Accepted Answer

Methanogenic Archaea

Question 7

Which of the following best explains why penicillin is effective against many bacteria but not against Archaea?

Accepted Answer

Penicillin inhibits peptide cross-linking in peptidoglycan, which is absent in Archaea.

Question 8

Which of the following transport mechanisms involves a series of proteins and chemical modification of the transported substance?

Accepted Answer

Group translocation

Question 9

A bacterial cell is exposed to human tears, which contain lysozyme. What is the most likely effect on the cell wall?

Accepted Answer

Lysozyme cleaves the glycosidic bonds in peptidoglycan, leading to cell lysis.

Question 10

Which of the following is a function of the S-layer in prokaryotic cells?

Accepted Answer

Protection from host defenses and maintaining cell shape

Question 11

Which of the following best describes the arrangement of hydrophobic and hydrophilic regions in a phospholipid bilayer?

Accepted Answer

Hydrophilic heads face both the cytoplasm and external environment, hydrophobic tails face inward

Question 12

Which of the following statements about porins is correct?

Accepted Answer

Porins are transmembrane proteins in the outer membrane of Gram-negative bacteria that allow solute passage.

Question 13

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

Accepted Answer

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

Question 14

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

Accepted Answer

Synthesis of ribosomal RNA

Question 15

A researcher observes a prokaryotic cell with an S-layer as its only cell envelope component outside the cytoplasmic membrane. This cell is most likely:

Accepted Answer

An archaeon

Question 16

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.

Question 17

Which of the following is true regarding the periplasmic space in Gram-negative bacteria?

Accepted Answer

It is located between the cytoplasmic membrane and the outer membrane.

Question 18

Which of the following best explains why lysozyme is an effective defense against bacterial infection in humans?

Accepted Answer

Lysozyme hydrolyzes the glycosidic bonds in peptidoglycan, weakening the bacterial cell wall.

Question 19

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

Accepted Answer

It chemically modifies the transported substance during passage.

Question 20

A bacterium is found to have a cell envelope with an outer membrane, a thin peptidoglycan layer, and LPS. Which of the following statements is true?

Accepted Answer

This bacterium is Gram-negative.

Microbial Cell Structure and Function: The Cell Envelope

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