Question 1

Which of the following best describes a virus?

Accepted Answer

A non-cellular infectious agent that requires a host cell to replicate

Question 2

Which of the following statements correctly distinguishes between an enveloped and a naked virus?

Accepted Answer

Enveloped viruses have a lipid membrane surrounding their capsid, while naked viruses lack this envelope

Question 3

A patient is diagnosed with HIV, a retrovirus. Which enzyme is crucial for the replication of this virus, and what is its function?

Accepted Answer

Reverse transcriptase; converts viral RNA into DNA

Question 4

Which of the following best describes the process of viral transduction?

Accepted Answer

The transfer of genetic material from one bacterium to another via a bacteriophage

Question 5

Which of the following is NOT a typical shape observed in viruses?

Accepted Answer

Cuboidal

Question 6

Why are antibiotics generally ineffective against viral infections?

Accepted Answer

Viruses lack the cellular structures targeted by antibiotics

Question 7

A laboratory technician performs a viral plaque assay. What does each plaque represent?

Accepted Answer

A single virus particle that has lysed a host cell

Question 8

Which of the following best describes a latent viral infection?

Accepted Answer

The virus remains dormant within the host cell and can reactivate later

Question 9

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that lack nucleic acids

Question 10

Penicillin is classified as which type of antibiotic, and what is its primary mode of action?

Accepted Answer

Narrow-spectrum; inhibits cell wall synthesis

Question 11

Which of the following best explains why tetracycline is effective against bacteria but not human cells?

Accepted Answer

Tetracycline targets the 70S ribosome found in bacteria, not the 80S ribosome in human cells

Question 12

A patient is prescribed a broad-spectrum antibiotic. What is a potential risk associated with this treatment?

Accepted Answer

It may disrupt normal microbiota, leading to secondary infections

Question 13

Which of the following best describes the function of beta-lactamase in bacteria?

Accepted Answer

It inactivates beta-lactam antibiotics like penicillin

Question 14

Which of the following is a key difference between semisynthetic and synthetic antibiotics?

Accepted Answer

Semisynthetic antibiotics are chemically modified natural compounds, while synthetic antibiotics are entirely man-made

Question 15

A physician wants to determine the minimum inhibitory concentration (MIC) of an antibiotic. What does the MIC represent?

Accepted Answer

The lowest concentration of antibiotic that inhibits visible growth of a microorganism

Question 16

Which of the following mechanisms can bacteria use to become resistant to antibiotics?

Accepted Answer

Producing enzymes that degrade the antibiotic

Question 17

How can plasmids contribute to the spread of antibiotic resistance among bacteria?

Accepted Answer

By carrying genes that encode resistance and transferring them via conjugation

Question 18

Which of the following is a requirement for an antibiotic to be considered effective?

Accepted Answer

It must selectively target the pathogen without harming the host

Question 19

A virus undergoes the lysogenic cycle. Which of the following events is characteristic of this cycle?

Accepted Answer

Integration of viral DNA into the host genome without immediate lysis

Question 20

A patient is given an antibiotic with a half-life of 8 hours. If the initial dose is 400 mg, how much of the drug remains in the body after 24 hours? Use the formula $$C = C_0$ 	imes (\frac{1}{2}$$)^{t/t_{1/2}$$}$$, where $$C_0 is $$the initial concentration, $$t is $$time elapsed, and $$t_{1/2} is $$the half-life.

Accepted Answer

$$C = 400 	imes (\frac{1}{2}$$)^{24/8}$$ = 400 	imes (\frac{1}{2})^3$ = 400 	imes \frac{1}{8} = 50 mg$$

Microbiology Study Guide: Viruses and Antibiotics – Step-by-Step Guidance

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