Question 1

Which of the following best explains why Gram-negative bacteria are often more resistant to antibiotics such as penicillin than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria have an outer membrane composed of lipopolysaccharides that restricts the entry of many antibiotics.

Question 2

A patient is accidentally infused with a hypertonic saline solution. What is the most likely effect on their red blood cells, and why?

Accepted Answer

The cells will shrink because water moves out of the cells into the hypertonic solution.

Question 3

Which structure is responsible for the motility of spirochetes such as Treponema pallidum, and how does it function?

Accepted Answer

Endoflagella; they rotate within the periplasmic space, causing the cell to corkscrew through its environment.

Question 4

Which of the following statements about the bacterial glycocalyx is TRUE?

Accepted Answer

It protects the cell from desiccation and helps in the formation of biofilms.

Question 5

During Gram staining, why do Gram-positive bacteria retain the crystal violet dye while Gram-negative bacteria do not?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer that retains the dye after decolorization.

Question 6

A bacterium is observed to move toward a chemical attractant in its environment. Which process best describes this movement?

Accepted Answer

Chemotaxis

Question 7

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

Accepted Answer

They are involved in the transfer of DNA between cells during conjugation.

Question 8

Which of the following is a key difference between the cell membranes of Archaea and Bacteria?

Accepted Answer

Archaeal membranes contain ether linkages, which are stronger and more stable at high temperatures, while bacterial membranes contain ester linkages.

Question 9

Which of the following best explains why endospores are significant in medical microbiology?

Accepted Answer

Endospores are highly resistant to heat, desiccation, and chemicals, making infections difficult to eradicate.

Question 10

A scientist is using a light microscope with a 40x objective lens and a 10x ocular lens. What is the total magnification being used?

Accepted Answer

$$40 	imes 10 = 400$$

Question 11

Which of the following is a function of the periplasmic space in Gram-negative bacteria?

Accepted Answer

It contains water, nutrients, and digestive enzymes involved in specific transport.

Question 12

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

Accepted Answer

It is a mesh-like complex of polysaccharides composed of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked by crossbridges of amino acids.

Question 13

Which of the following is a unique feature of eukaryotic cells compared to prokaryotic cells?

Accepted Answer

Presence of membrane-bound organelles such as mitochondria and endoplasmic reticulum.

Question 14

A bacterial cell is placed in a hypotonic solution. What will most likely happen to the cell if it has an intact cell wall?

Accepted Answer

The cell will swell but not burst because the cell wall prevents lysis.

Question 15

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

Accepted Answer

They provide a negative electrical charge to the cell surface and may play a role in ion passage.

Question 16

Which of the following is TRUE regarding the endosymbiotic theory for the origin of eukaryotic organelles?

Accepted Answer

It proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by an ancestral eukaryotic cell.

Question 17

Which of the following best describes facilitated diffusion across a cell membrane?

Accepted Answer

Movement of molecules down their concentration gradient through a membrane protein without energy expenditure.

Question 18

Which of the following is a distinguishing feature of archaeal cell walls compared to bacterial cell walls?

Accepted Answer

Archaeal cell walls lack peptidoglycan and may contain polysaccharides, proteins, or pseudomurein.

Question 19

Which of the following best describes the function of the Golgi body in eukaryotic cells?

Accepted Answer

It receives, processes, and packages large molecules for export from the cell.

Prokaryotic and Eukaryotic Cell Structure: Cell Walls, Membranes, and Surface Structures

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