Question 1

Which of the following best explains why electron microscopes have a higher resolving power than light microscopes?

Accepted Answer

They use shorter wavelengths of electrons, which increases resolving power according to $$d = \frac{\lambda}{2NA}.$$

Question 2

A microbiologist wants to observe the surface structure of a virus particle at nanometer resolution. Which microscope should they use and why?

Accepted Answer

Scanning electron microscope, because it provides detailed 3D images of surfaces at high resolution.

Question 3

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

Accepted Answer

Gram-positive bacteria retain the crystal violet stain after decolorization and appear purple.

Question 4

A student is using a compound bright-field microscope with an objective lens of 40x and an ocular lens of 10x. What is the total magnification?

Accepted Answer

$$400	imes$$

Question 5

Why is oil immersion used with the 100x objective lens in light microscopy?

Accepted Answer

It increases the numerical aperture by reducing light refraction, improving resolution.

Question 6

Which of the following best describes the relationship between wavelength and resolving power in microscopy?

Accepted Answer

Shorter wavelengths result in greater resolving power, as shown by $$d = \frac{\lambda}{2NA}.$$

Question 7

A sample of bacteria is stained with a basic dye. What is the most likely reason for this choice?

Accepted Answer

Bacterial cells have a net negative charge, so basic dyes (which are positively charged) bind to them.

Question 8

Which of the following is NOT a type of light microscope?

Accepted Answer

Transmission electron microscope

Question 9

A researcher wants to observe living, unstained cells to study their motility. Which microscope is most appropriate?

Accepted Answer

Phase-contrast microscope

Question 10

Which of the following best explains why contrast is important in microscopy?

Accepted Answer

Contrast allows for distinguishing between the specimen and the background, making structures visible.

Question 11

Which step in the Gram stain procedure is responsible for differentiating between Gram-positive and Gram-negative bacteria?

Accepted Answer

Decolorization with alcohol or acetone

Question 12

A microbiologist is using a scanning probe microscope (AFM) to study a sample. What is a unique capability of this microscope?

Accepted Answer

It can measure attractive and propulsive forces at the atomic level.

Question 13

Which of the following best describes the arrangement of cocci in a staphylococcus sample?

Accepted Answer

Grape-like clusters

Question 14

Which of the following is a correct statement about the morphology of prokaryotic cells?

Accepted Answer

Prokaryotic cells can be found in a variety of shapes, including cocci, bacilli, and spirilla.

Question 15

A student observes a bacterial sample under the microscope and notes the presence of rod-shaped cells arranged in chains. What is the correct term for this arrangement?

Accepted Answer

Streptobacilli

Question 16

Which of the following best describes the process of 'snapping division' in prokaryotes?

Accepted Answer

A variation of binary fission where tension causes the outer cell wall to snap, leaving daughter cells attached.

Question 17

Which of the following is a key difference between simple and differential stains?

Accepted Answer

Differential stains distinguish between different types of bacteria, while simple stains do not.

Question 18

A microbiologist is preparing a slide for Gram staining. What is the first step after preparing the smear?

Accepted Answer

Heat-fix the smear to the slide.

Question 19

Which of the following best explains why shorter wavelengths of light provide greater resolving power in microscopy?

Accepted Answer

Shorter wavelengths decrease the value of $$d in$$ $$d = \frac{\lambda}{2NA}$$, allowing smaller objects to be distinguished.

Question 20

Which of the following is a limitation of bright-field microscopy when observing live, unstained specimens?

Accepted Answer

Live, unstained specimens often lack contrast and are difficult to see.

Microscopy and Prokaryotic Cell Morphology: Study Notes for Microbiology

Study Guide - Practice Questions

Study Guide - Flashcards