Question 1

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

Accepted Answer

Gram-negative bacteria possess an outer membrane that acts as a permeability barrier, limiting antibiotic access to the peptidoglycan.

Question 2

A patient is given a hypotonic intravenous solution by mistake. What is the most likely effect on their red blood cells, and which bacterial structure provides similar protection in bacteria?

Accepted Answer

Red blood cells will burst (lyse); the bacterial cell wall provides similar protection against osmotic lysis.

Question 3

Which of the following best describes the function of hopanoids in bacterial plasma membranes?

Accepted Answer

Hopanoids stabilize the membrane, similar to the role of cholesterol in eukaryotes.

Question 4

A microbiologist isolates a microorganism from acidic soil that lacks peptidoglycan in its cell wall and is not pathogenic. Which domain does this organism most likely belong to?

Accepted Answer

Archaea

Question 5

Which of the following is a correct sequence of steps in the Gram staining procedure?

Accepted Answer

Fixation → Crystal violet → Iodine → Decolorization → Safranin

Question 6

Which of the following best explains why Mycobacteria are acid-fast and resistant to desiccation?

Accepted Answer

They possess mycolic acids in their cell wall, making it waxy and impermeable.

Question 7

A scientist discovers a new microorganism that is unicellular, has chitin in its cell wall, and absorbs organic chemicals for energy. Which group does it most likely belong to?

Accepted Answer

Fungi (yeast)

Question 8

Which of the following best describes the mechanism of action of lysozyme on bacterial cell walls?

Accepted Answer

Lysozyme hydrolyzes the $$\beta-1$$,4 glycosidic bonds between N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).

Question 9

Which of the following is a unique feature of bacterial endospores that contributes to their extreme resistance?

Accepted Answer

High content of dipicolinic acid (DPA) and $$\mathrm{Ca$$^{2+}$$}$$

Question 10

A bacterium is observed to move toward a chemical attractant by alternating between 'runs' and 'tumbles.' What is the energy source for the rotation of its flagella?

Accepted Answer

Proton motive force ($$\Delta p)$$

Question 11

Which of the following best explains why penicillin is more effective against actively growing Gram-positive bacteria than against Gram-negative bacteria?

Accepted Answer

Penicillin inhibits the formation of peptide cross-bridges in peptidoglycan, which is more abundant in Gram-positive bacteria.

Question 12

Which of the following is a function of the bacterial capsule?

Accepted Answer

Protects against phagocytosis and desiccation

Question 13

A researcher is studying a bacterium that can survive in extremely salty environments and lacks peptidoglycan in its cell wall. Which of the following best describes its cell wall composition?

Accepted Answer

Cell wall made of pseudomurein

Question 14

Which of the following statements about plasmids is correct?

Accepted Answer

Plasmids are extrachromosomal DNA elements that can carry antibiotic resistance genes.

Question 15

Which of the following best describes the difference between simple diffusion and facilitated diffusion across the bacterial plasma membrane?

Accepted Answer

Simple diffusion involves movement of solutes directly through the lipid bilayer, while facilitated diffusion requires transporter proteins.

Question 16

A Gram-negative bacterium is placed in a hypertonic solution. What is the most likely outcome for the cell?

Accepted Answer

The cell will undergo plasmolysis as water leaves the cytoplasm.

Question 17

Which of the following is a correct pairing of a bacterial structure and its function?

Accepted Answer

Pili – DNA transfer during conjugation

Question 18

Which of the following best explains why endospores are important in the food industry?

Accepted Answer

Endospores can survive standard cooking and food preservation methods, leading to potential foodborne illness.

Question 19

Which of the following statements about the human microbiome is correct?

Accepted Answer

The human microbiome helps maintain health and can prevent the growth of pathogens.

Question 20

A bacterial cell is treated with penicillin while in a hypotonic solution. What is the most likely outcome, and why?

Accepted Answer

The cell will undergo osmotic lysis because penicillin weakens the cell wall, allowing water influx to burst the cell.

Microbiology Study Guide: Introduction, Cell Structure, and Functional Anatomy

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