Question 1

Which of the following best explains why the cytoplasmic (cell) membrane is an effective barrier to ions and polar molecules?

Accepted Answer

The hydrophobic core of the phospholipid bilayer blocks ions and polar molecules.

Question 2

A bacterium is found to have a thick peptidoglycan layer, teichoic acids, and no outer membrane. Which of the following is most likely true about this organism?

Accepted Answer

It is Gram-positive and likely stains purple in a Gram stain.

Question 3

Which component of the Gram-negative outer membrane is responsible for its endotoxin activity?

Accepted Answer

Lipid A

Question 4

A scientist treats a bacterial culture with lysozyme and observes cell lysis. Which chemical bond is most likely being targeted?

Accepted Answer

β-1,4 glycosidic bonds in peptidoglycan

Question 5

Which of the following structures is found only in Gram-negative bacteria and not in Gram-positive bacteria?

Accepted Answer

Outer membrane containing LPS

Question 6

Methanogenic Archaea are resistant to both lysozyme and penicillin. What is the main reason for this resistance?

Accepted Answer

Their cell wall contains β-1,3 bonds and all L-amino acids.

Question 7

Which of the following best describes the function of gas vesicles in aquatic bacteria?

Accepted Answer

They provide buoyancy to optimize light and nutrient access.

Question 8

A patient is infected with a bacterium that forms a polysaccharide capsule. Which of the following is a likely consequence?

Accepted Answer

The bacterium is better able to evade the host immune system.

Question 9

Which of the following statements about endospores is correct?

Accepted Answer

They are survival structures found only in Gram-positive bacteria.

Question 10

A researcher observes a bacterium with peritrichous flagella. Which of the following best describes its motility?

Accepted Answer

It moves using multiple flagella distributed over the entire cell surface.

Question 11

Which of the following is a key piece of evidence supporting the endosymbiotic theory for the origin of mitochondria?

Accepted Answer

Circular DNA and bacterial-like ribosomes

Question 12

Which of the following best distinguishes bacterial fimbriae from pili?

Accepted Answer

Fimbriae are for attachment, while pili are involved in conjugation.

Question 13

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

Accepted Answer

Ether-linked isoprenoid chains

Question 14

A Gram-negative bacterium is found to be resistant to penicillin. Which structural feature most likely contributes to this resistance?

Accepted Answer

Presence of an outer membrane that restricts antibiotic entry

Question 15

Which of the following best describes the arrangement and shape of Staphylococcus as seen under a microscope?

Accepted Answer

Spherical cells in clusters

Question 16

Which of the following is a function of the S-layer found in some Bacteria and Archaea?

Accepted Answer

Protein or glycoprotein lattice for protection and adhesion

Question 17

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

Accepted Answer

They lack a cell wall entirely.

Question 18

Which of the following is a correct match between a genus and its Gram reaction, shape, and arrangement?

Accepted Answer

Streptococcus: Gram-positive, cocci, chains

Question 19

Which of the following is a primary function of magnetosomes in certain bacteria?

Accepted Answer

Magnetotaxis (orientation along magnetic fields)

Question 20

Which of the following best describes the energy source for bacterial flagellar rotation?

Accepted Answer

Proton motive force

Microbial Cell Structure and Function: Study Guide

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