Question 1

Which of the following best describes the principle demonstrated by Louis Pasteur's swan-neck flask experiment?

Accepted Answer

It disproved spontaneous generation by showing that microbes come from the environment, not from spontaneous creation.

Question 2

A patient is diagnosed with a bacterial infection. According to Koch's postulates, which step is necessary to confirm that a specific bacterium is the cause of the disease?

Accepted Answer

The bacterium must be isolated from the diseased host and grown in pure culture.

Question 3

Which of the following best describes the difference between Gram-positive and Gram-negative bacterial cell envelopes?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing LPS.

Question 4

A scientist is using a microscope to observe the surface details of a virus particle at very high resolution. Which technique is most appropriate for this purpose?

Accepted Answer

Scanning electron microscopy (SEM)

Question 5

Which of the following statements about facilitated diffusion and active transport is correct?

Accepted Answer

Facilitated diffusion moves substances down their concentration gradient without energy input, while active transport moves substances against their gradient using energy.

Question 6

Which of the following best describes the function of siderophores in bacterial physiology?

Accepted Answer

They are molecules that bind and transport iron into bacterial cells.

Question 7

A bacterial cell is placed in a hypertonic solution. Which process will occur as a result of osmosis?

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 8

Which of the following best describes the role of the proton motive force ($$\Delta p) in $$bacterial cells?

Accepted Answer

It drives the rotation of flagella and ATP synthesis via ATP synthase.

Question 9

Which of the following is a correct pairing of microbial energy and electron sources?

Accepted Answer

Lithotroph: uses inorganic molecules as an electron source

Question 10

A researcher is studying a bacterial population that enters a stationary phase after rapid growth. Which of the following best explains the stationary phase?

Accepted Answer

Nutrient depletion and waste accumulation cause the rate of cell division to equal the rate of cell death.

Question 11

Which of the following statements about the Gram stain is correct?

Accepted Answer

It differentiates bacteria based on the thickness of their peptidoglycan layer.

Question 12

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

Accepted Answer

It protects the cell from phagocytosis and desiccation.

Question 13

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause neurodegenerative diseases.

Question 14

A virus with a single-stranded positive-sense RNA genome infects a host cell. Which of the following best describes the first step in its replication cycle?

Accepted Answer

The viral RNA is directly translated by host ribosomes to produce viral proteins.

Question 15

Which of the following best describes the mechanism of CRISPR-Cas immunity in bacteria?

Accepted Answer

Cas proteins use CRISPR-derived RNA to recognize and cleave foreign DNA.

Question 16

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 them difficult to eliminate.

Question 17

A patient is infected with a retrovirus. Which enzyme is essential for the replication of the viral genome?

Accepted Answer

Reverse transcriptase

Question 18

Which of the following best describes the difference between lysogenic and lytic cycles in bacteriophages?

Accepted Answer

In the lysogenic cycle, the phage genome is replicated along with the host genome without killing the host cell.

Question 19

Which of the following best describes the function of a plaque assay in virology?

Accepted Answer

It quantifies the number of infectious viral particles by counting clear zones formed on a lawn of host cells.

Question 20

A microbiologist is using a differential stain to distinguish between two types of bacteria. Which of the following is a key feature of differential stains?

Accepted Answer

They rely on differences in cell wall structure to produce different staining outcomes.

Microbiology Exam I Study Guide: Chapters 1–6

Study Guide - Practice Questions

Study Guide - Flashcards