Question 1

Which of the following best explains why Gram-negative bacteria are generally more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

Their outer membrane contains lipopolysaccharide (LPS), which acts as a permeability barrier.

Question 2

A researcher isolates a microorganism with a cell wall composed of pseudomurein. Which of the following characteristics would you expect this organism to have?

Accepted Answer

It is insensitive to lysozyme and penicillin.

Question 3

Which of the following structures is primarily responsible for the selective permeability of the bacterial cell membrane?

Accepted Answer

Phospholipid bilayer with embedded proteins

Question 4

A Gram-positive bacterium is exposed to lysozyme. What is the most likely outcome, and why?

Accepted Answer

The cell wall will be degraded because lysozyme cleaves the β-1,4 glycosidic bonds in peptidoglycan.

Question 5

Which of the following best describes the function of bacterial capsules?

Accepted Answer

They assist in attachment to surfaces and protect against phagocytosis.

Question 6

A bacterium is observed to move toward a source of glucose in its environment. Which process is responsible for this behavior?

Accepted Answer

Chemotaxis

Question 7

Which of the following statements about archaeal membranes is correct?

Accepted Answer

They contain ether-linked isoprenoid chains and can form monolayers.

Question 8

Which of the following is a unique feature of endospores that contributes to their resistance to heat and chemicals?

Accepted Answer

High concentration of dipicolinic acid complexed with Ca$^{2+}$

Question 9

A Gram-negative bacterium is found to be highly virulent due to its ability to avoid host immune responses. Which cell envelope component is most likely responsible for this property?

Accepted Answer

Lipopolysaccharide (LPS), specifically the O-polysaccharide

Question 10

Which of the following best describes the arrangement and function of flagella in peritrichously flagellated bacteria?

Accepted Answer

Flagella are distributed over the entire cell surface and allow 'run and tumble' motility.

Question 11

Which of the following is a correct statement about the structure of peptidoglycan in bacterial cell walls?

Accepted Answer

It is composed of alternating N-acetylglucosamine and N-acetylmuramic acid linked by β-1,4 glycosidic bonds.

Question 12

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 13

A bacterium is observed to form a pellicle (thin sheet of cells) on the surface of a liquid medium. Which structure is most likely involved in this process?

Accepted Answer

Fimbriae

Question 14

Which of the following is a function of poly-β-hydroxybutyric acid (PHB) inclusions in bacteria?

Accepted Answer

Energy and carbon storage

Question 15

Which of the following best describes the process of conjugation in bacteria?

Accepted Answer

Transfer of genetic material via sex pili between two cells

Question 16

A bacterium is found to contain magnetosomes. What is the most likely function of these structures?

Accepted Answer

Orientation and movement along magnetic field lines

Question 17

Which of the following is a distinguishing feature of the S-layer in some prokaryotes?

Accepted Answer

It is a paracrystalline protein or glycoprotein layer that provides structural strength and protection.

Question 18

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

Accepted Answer

They provide rigidity to the cell wall and can bind cations.

Question 19

Which of the following is a correct statement about the endosymbiotic hypothesis for the origin of mitochondria and chloroplasts?

Accepted Answer

Mitochondria and chloroplasts descended from bacterial cells that formed symbiotic relationships with early eukaryotes.

Microbial Cell Structure and Function: Study Guide

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