Question 1

Which of the following best explains why scientists prefer the metric system over the English system for scientific measurements?

Accepted Answer

The metric system is based on multiples of ten, making calculations and conversions simpler.

Question 2

A microbiologist is using a compound light microscope with a 40x objective lens and a 10x ocular lens. What is the total magnification being used?

Accepted Answer

$40 	imes 10 = 400$

Question 3

Which property of a microscope determines its ability to distinguish two points that are very close together?

Accepted Answer

Resolution

Question 4

Why does using immersion oil with a 100x objective lens improve the resolution of a light microscope?

Accepted Answer

Immersion oil reduces light refraction, allowing more light to enter the objective lens.

Question 5

A scientist wants to observe living, unstained cells to study their movement. Which type of microscope should they use?

Accepted Answer

Phase-contrast microscope

Question 6

Which of the following statements about electron microscopes is correct?

Accepted Answer

They use electron beams instead of light to achieve higher resolution.

Question 7

A Gram-negative bacterium appears colorless after the decolorization step in Gram staining. Why?

Accepted Answer

The thin peptidoglycan layer cannot retain the crystal violet-iodine complex after decolorization.

Question 8

Which staining technique would be most appropriate to identify Mycobacterium tuberculosis in a sputum sample?

Accepted Answer

Acid-fast stain

Question 9

A researcher is using a dichotomous key to identify an unknown microorganism. What is the main feature of a dichotomous key?

Accepted Answer

It presents a series of paired statements, each with two choices.

Question 10

Which of the following best describes the principle behind immunofluorescence microscopy?

Accepted Answer

Antibodies labeled with fluorescent dyes bind to specific antigens, allowing visualization under UV light.

Question 11

Which of the following is a key advantage of using MALDI/TOF mass spectrometry in microbial identification?

Accepted Answer

It rapidly identifies microbes by analyzing their unique protein profiles.

Question 12

Which of the following stains would be most appropriate to visualize bacterial capsules?

Accepted Answer

Negative stain

Question 13

A scientist is comparing the G+C content of two bacterial species. What is the purpose of this analysis?

Accepted Answer

To help classify and identify prokaryotes based on their nucleic acid composition.

Question 14

Which of the following best explains why color is absent in an unretouched electron micrograph?

Accepted Answer

Electron microscopes use electrons, not light, so images are produced in grayscale.

Question 15

Which of the following is a correct statement about the use of basic and acidic dyes in staining?

Accepted Answer

Basic dyes stain acidic structures, and are more commonly used because most cells are negatively charged.

Question 16

A hospital lab is trying to quickly identify a bacterial pathogen from a patient sample. Which method would provide the fastest and most specific identification?

Accepted Answer

MALDI/TOF mass spectrometry

Question 17

Which of the following is NOT a characteristic used in modern microbial taxonomy?

Accepted Answer

Ability to cause disease in humans

Question 18

Why did Linnaeus not create taxonomic groups for viruses?

Accepted Answer

Viruses were not known or understood at the time Linnaeus developed his system.

Question 19

Which type of microscopy would be best for visualizing the surface details of a virus particle?

Accepted Answer

Scanning electron microscopy (SEM)

Question 20

A clinical sample is tested with a serological agglutination test. What is being detected in this test?

Accepted Answer

The presence of specific antigens or antibodies causing visible clumping.

Ch.4 - Microscopy, Staining, and Classification in Microbiology

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