Question 1

Which of the following best explains why penicillin is selectively toxic to bacteria but not to human cells?

Accepted Answer

Penicillin targets the synthesis of peptidoglycan, which is present in bacterial cell walls but absent in human cells.

Question 2

A patient is prescribed a broad-spectrum antibiotic. Which of the following is a potential negative consequence of this treatment?

Accepted Answer

It may disrupt the normal microbiota, leading to secondary infections such as Clostridioides difficile.

Question 3

During the Kirby-Bauer disk diffusion test, a large zone of inhibition is observed around an antibiotic disk. What does this indicate?

Accepted Answer

The bacteria are highly susceptible to the antibiotic.

Question 4

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

Accepted Answer

Uptake of naked DNA from the environment and incorporation into the bacterial chromosome.

Question 5

A bacterial culture is placed in a hypertonic solution. What is the most likely outcome for the cells?

Accepted Answer

Water will flow out of the cells, causing plasmolysis.

Question 6

Which of the following statements about biofilms is TRUE?

Accepted Answer

Bacteria in biofilms are up to 1,000 times more resistant to antibiotics than planktonic (free-living) cells.

Question 7

A microbiologist wants to sterilize a solution that is heat-sensitive. Which method is most appropriate?

Accepted Answer

Filtration through a membrane with pores smaller than $$0.22\ \mu m$$

Question 8

Which of the following is a key difference between algae and fungi?

Accepted Answer

Algae are autotrophic and have cell walls made of cellulose, while fungi are heterotrophic and have cell walls made of chitin.

Question 9

Which of the following best describes the function of the F plasmid in bacterial conjugation?

Accepted Answer

It carries genes for the formation of the sex pilus and allows transfer of DNA between cells.

Question 10

A patient is diagnosed with a fungal infection. Which of the following drug classes would most likely be prescribed to target the unique component of fungal cell membranes?

Accepted Answer

Azoles, which inhibit ergosterol synthesis.

Question 11

Which of the following statements about prions is CORRECT?

Accepted Answer

Prions are infectious proteins that lack nucleic acids and cause neurodegenerative diseases.

Question 12

A bacterial cell is exposed to UV light, which causes the formation of thymine dimers. What is the most likely effect on the cell?

Accepted Answer

DNA replication and transcription will be disrupted, potentially leading to mutations.

Question 13

Which of the following is a correct sequence of events in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment → Penetration → Biosynthesis → Assembly → Release

Question 14

A patient with tuberculosis is treated with rifampin. What is the mechanism of action of this drug?

Accepted Answer

It inhibits RNA polymerase, blocking transcription.

Question 15

Which of the following best explains why enveloped viruses are generally less resistant to disinfectants than nonenveloped (naked) viruses?

Accepted Answer

The lipid envelope is easily disrupted by detergents and alcohols, inactivating the virus.

Question 16

A bacterial culture is in the log (exponential) phase of growth. Which of the following is TRUE about the cells at this stage?

Accepted Answer

They are dividing at their maximum rate and are most susceptible to antibiotics.

Question 17

Which of the following is a characteristic of protozoa that distinguishes them from bacteria?

Accepted Answer

Protozoa are eukaryotic and lack a cell wall, while bacteria are prokaryotic and usually have a cell wall.

Question 18

A microbiologist is using MacConkey agar to isolate bacteria from a clinical sample. Which of the following best describes this medium?

Accepted Answer

It is both selective (inhibits gram-positives) and differential (lactose fermenters turn pink).

Question 19

Which of the following mechanisms can lead to acquired antimicrobial resistance in bacteria?

Accepted Answer

Production of enzymes that inactivate the drug, such as beta-lactamase.

Question 20

A scientist is studying a lichen on a rock. Which of the following best describes the mutualistic relationship in a lichen?

Accepted Answer

The fungus provides structure and absorbs minerals, while the alga or cyanobacterium performs photosynthesis to provide nutrients.

BIO 150 – Microbiology Exam 2 Study Guide (Chapters 6, 7, 8, 12, 13, 20)

Study Guide - Practice Questions

Study Guide - Flashcards