Question 1

Which of the following best describes the relationship between magnification and field of view in a compound light microscope?

Accepted Answer

As magnification increases, the field of view decreases.

Question 2

A student is preparing a bacterial smear. After air drying the smear, what is the next critical step before staining?

Accepted Answer

Heat fix the cells by passing the slide through a flame.

Question 3

Which of the following is NOT a correct lab safety rule for microbiology labs?

Accepted Answer

Eating snacks at your bench.

Question 4

What is the function of the mordant (Gram’s iodine) in the Gram staining procedure?

Accepted Answer

To form an insoluble complex with crystal violet, locking it inside the cell.

Question 5

Which genus of bacteria is known for forming endospores and causing diseases such as anthrax and tetanus?

Accepted Answer

Bacillus

Question 6

Which of the following best explains why oil immersion is used with the 100x objective lens in light microscopy?

Accepted Answer

Oil has the same refractive index as glass, reducing light bending and increasing resolution.

Question 7

Which of the following statements about Gram-negative bacteria is correct?

Accepted Answer

They lose the primary stain during decolorization and take up the pink/red counterstain.

Question 8

A microbiologist wants to isolate halophilic bacteria from a mixed sample. Which agar should they use and why?

Accepted Answer

Mannitol salt agar, because its high NaCl concentration selects for salt-loving bacteria.

Question 9

Which of the following best describes a differential staining technique?

Accepted Answer

A technique that uses multiple dyes to distinguish between different groups of organisms.

Question 10

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

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 11

A student observes a bacterial sample under the microscope after Gram staining. The cells appear pink. What can be concluded about the cell wall structure?

Accepted Answer

The bacteria are Gram-negative with a thin peptidoglycan layer and an outer membrane.

Question 12

Which of the following best describes the term 'ubiquitous' as it applies to bacteria?

Accepted Answer

Bacteria are found everywhere on Earth and are highly adaptable.

Question 13

Which of the following is a correct statement about MacConkey agar?

Accepted Answer

It selects for Gram-negative bacteria and differentiates lactose fermenters.

Question 14

Which of the following is NOT a type of hazard commonly encountered in a microbiology laboratory?

Accepted Answer

Electrical hazards from using microscopes

Question 15

Which of the following best describes the purpose of heat fixing a bacterial smear?

Accepted Answer

To kill the bacteria and adhere them to the slide.

Question 16

Which of the following equations correctly represents the calculation of total magnification in a compound microscope?

Accepted Answer

$$	ext{Total Magnification} = 	ext{Objective Magnification} 	imes 	ext{Ocular Magnification}$$

Question 17

Which of the following best describes the depth of field in microscopy?

Accepted Answer

The distance from the nearest object plane in focus to the farthest object plane that is simultaneously in focus.

Question 18

Which of the following is the correct sequence for the '5 I’s' in microbiology?

Accepted Answer

Inoculation, Incubation, Isolation, Inspection, Identification

Question 19

Which of the following diseases is NOT caused by an endospore-forming bacterium?

Accepted Answer

Tuberculosis

Question 20

A microbiologist observes a slide under 1000x magnification using oil immersion. What is the main reason for using oil at this magnification?

Accepted Answer

To match the refractive index of glass and reduce light refraction, improving resolution.

Microscopy, Cell Domains, Staining, and Viruses: Microbiology Study Guide

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