Question 1

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

Accepted Answer

Electron microscopes use electrons instead of photons, which have shorter wavelengths.

Question 2

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

Accepted Answer

Scanning electron microscope (SEM)

Question 3

Which statement about the Gram stain procedure is correct?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet stain.

Question 4

What is the main reason staining is used in light microscopy?

Accepted Answer

To increase contrast and resolution by coloring specimens

Question 5

Which formula correctly represents the relationship between resolution ($$d$$), wavelength ($$\lambda$$), and numerical aperture ($$NA) in $$microscopy?

Accepted Answer

$$d = \frac{\lambda}{2NA}$$

Question 6

A student observes bacteria under a bright-field microscope and notices poor contrast. Which technique would best improve the visibility of the bacteria?

Accepted Answer

Use a simple stain such as methylene blue

Question 7

Why do all prokaryotic cells have a negative charge, and how does this affect staining?

Accepted Answer

Their cell walls contain negatively charged molecules, which attract basic dyes.

Question 8

Which of the following best describes the principle of refraction in microscopy?

Accepted Answer

Refraction is the bending of light as it passes from one medium to another, which enables magnification.

Question 9

A microbiologist is using a fluorescence microscope to visualize bacteria. What is the main advantage of this technique?

Accepted Answer

It enables specific labeling of cellular components using fluorescent dyes.

Question 10

Which arrangement of cocci is described as grape-like clusters?

Accepted Answer

Staphylococcus

Question 11

During binary fission, what is the primary event that leads to the formation of two daughter cells?

Accepted Answer

The cell wall snaps due to increased tension after septum formation.

Question 12

Which type of microscope would be best for measuring attractive and propulsive forces at the molecular level?

Accepted Answer

Scanning probe/atomic force microscope (AFM)

Question 13

Which of the following is NOT a step in the Gram stain procedure?

Accepted Answer

Application of methylene blue

Question 14

A sample contains rod-shaped bacteria arranged in chains. What is the correct term for this arrangement?

Accepted Answer

Streptobacilli

Question 15

Which property of light is most important for achieving high resolution in microscopy?

Accepted Answer

Short wavelength

Question 16

Why is oil immersion used with high-power objectives in light microscopy?

Accepted Answer

Oil decreases refraction, allowing more light to enter the objective lens.

Question 17

Which of the following is a correct statement about phase-contrast microscopy?

Accepted Answer

It enhances contrast by amplifying differences in refractive index.

Question 18

A microbiologist wants to distinguish between live and dead bacteria in a sample. Which staining technique would be most appropriate?

Accepted Answer

Fluorescent viability stain

Question 19

Which of the following best describes the arrangement of cocci in pairs?

Accepted Answer

Diplococcus

Question 20

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

Accepted Answer

Alcohol decolorization

Microscopy and Prokaryotic Cell Morphology: Study Notes for Microbiology

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