Quiz: Cell Biology Microscopy Techniques — 14 questions

1. What does magnification measure in microscopy?

A. The wavelength range emitted by the microscope

B. The minimum distance at which two objects can be distinguished

C. The amount of light absorbed by the specimen

D. The ratio between an observed dimension and the object's actual size

Answer: (D)

Explanation

Magnification expresses how the observed dimension compares with the object's actual size. Resolution is the property that determines whether two nearby objects can be distinguished, so it is not measured as a size ratio.

2. A microscope can produce a very large image, but two nearby points still appear as one blurred point. Which property is limiting the observation?

A. Illumination, because it determines the specimen's physical size

B. Resolution, because it determines the minimum separable distance

C. Magnification, because it determines the image enlargement

D. Contrast, because it determines the lens's numerical aperture

Answer: (B)

Explanation

Resolution limits whether two objects separated by a small distance can be distinguished, even when magnification is high. Magnification enlarges the image but does not by itself separate unresolved details.

3. Which comparison correctly distinguishes visible transmitted light microscopy from fluorescence microscopy?

A. Visible microscopy uses electron beams, whereas fluorescence microscopy uses transmitted white light

B. Visible microscopy uses one monochromatic wavelength in air, whereas fluorescence microscopy uses polychromatic light

C. Visible microscopy uses polychromatic light in air, whereas fluorescence microscopy uses one monochromatic wavelength

D. Visible microscopy uses fluorescent labels, whereas fluorescence microscopy uses unfiltered polychromatic light

Answer: (C)

Explanation

Visible transmitted light microscopy uses polychromatic light in air, while fluorescence microscopy uses a single monochromatic wavelength. The alternative descriptions reverse or replace these defining illumination characteristics.

4. What is the resolution limit of visible light microscopy?

A. 2 millimeters

B. 0.3 nanometers

C. 200 nanometers

D. 20 micrometers

Answer: (C)

Explanation

Visible light microscopy has a resolution limit of 200 nanometers. A value near 0.3 nanometer or less is associated with electron microscopy rather than visible light microscopy.

5. What does confocal fluorescence microscopy enable when imaging a thick specimen?

A. Polychromatic illumination can remove the need for fluorescence

B. Electron-scale detail can be obtained from transmitted visible light

C. Thin optical slices can be combined into a three-dimensional image

D. A single broad image can replace the need for depth information

Answer: (C)

Explanation

Confocal fluorescence microscopy divides a specimen into thin optical slices that can be recombined to reconstruct a three-dimensional image. A single broad image does not provide the same depth-resolved reconstruction.

6. Which feature most directly distinguishes confocal fluorescence microscopy from conventional visible microscopy?

A. It enlarges images without changing the ability to separate nearby objects

B. It measures specimen dimensions without using an optical image

C. It illuminates specimens with polychromatic light traveling through air

D. It produces thin optical sections suitable for three-dimensional reconstruction

Answer: (D)

Explanation

Confocal fluorescence microscopy generates thin optical sections that can be assembled into a three-dimensional representation. Conventional visible microscopy does not provide this same optical-slicing and reconstruction capability.

7. Which distinction correctly compares photon microscopy with electron microscopy?

A. Photon microscopy and electron microscopy both detect photons, but electron microscopy provides greater magnification through shorter wavelengths.

B. Photon microscopy detects photons and resolves about 200 nanometers, whereas electron microscopy detects electrons and reaches 0.3 nanometer or less.

C. Photon microscopy detects electrons and resolves about 200 nanometers, whereas electron microscopy detects photons and reaches 0.3 nanometer or less.

D. Photon microscopy detects photons and reaches 0.3 nanometer or less, whereas electron microscopy detects electrons and resolves about 200 nanometers.

Answer: (B)

Explanation

Photon microscopy forms information from detected photons and has a resolution limit near 200 nanometers, while electron microscopy detects electrons and can reach 0.3 nanometer or less. The second option reverses which type of signal each technique detects.

8. A researcher needs to distinguish the detected signal used by two microscopy methods; which pairing is correct?

A. Photon microscopy uses heavy-metal replicas, while electron microscopy uses fluorescent dyes.

B. Photon microscopy uses surface ions, while electron microscopy uses emitted photons.

C. Photon microscopy uses transmitted electrons, while electron microscopy uses reflected photons.

D. Photon microscopy uses detected photons, while electron microscopy uses detected electrons.

Answer: (D)

Explanation

The defining signal distinction is that photon microscopy detects photons and electron microscopy detects electrons. Transmitted electrons describe a mode within electron microscopy, not the signal used by photon microscopy.

9. How does transmission electron microscopy form its image?

A. It excites the entire sample surface and detects electrons passing through non-opacified regions to form one image.

B. It detects photons passing through an untreated specimen and reconstructs several surface views.

C. It scans the sample progressively with a mobile beam and detects signals emitted above the surface.

D. It illuminates a frozen replica and records shadows cast by platinum or silver deposits.

Answer: (A)

Explanation

TEM excites the entire surface and produces a single image from electrons transmitted through non-opacified regions. Progressive scanning with signals detected above the surface describes SEM instead.

10. Which sequence best describes preparation of a biological sample for TEM sectioning of subcellular structures?

A. Freezing, progressive surface scanning, photon detection, and image stacking.

B. Cryofracture, surface sublimation, metal shadowing, and replica removal.

C. Fixation, dehydration, resin embedding, thin sectioning, and opacification.

D. Dehydration, cryofracture, fluorescent labeling, thick sectioning, and sublimation.

Answer: (C)

Explanation

TEM section preparation proceeds through fixation, dehydration, resin embedding, thin sectioning, and opacification. Cryofracture followed by sublimation and metal shadowing is the preparation approach associated with SEM replicas.

11. What is the purpose of immunogold in TEM preparation?

A. It replaces resin embedding so that thick biological tissue can resist the vacuum.

B. It produces a mobile electron beam that scans the sample progressively.

C. It localizes a protein of interest within the electron-microscope specimen.

D. It creates a three-dimensional replica of the specimen surface after freezing.

Answer: (C)

Explanation

Immunogold is an opacification method in TEM that marks and localizes a protein of interest. Producing a three-dimensional surface replica through freezing and shadowing is associated with SEM preparation.

12. How does scanning electron microscopy generate information from a specimen?

A. The entire surface is excited at once, and electrons transmitted through non-opacified regions form one image.

B. A thin resin section is illuminated with photons, and transmitted light forms the image.

C. A frozen specimen is dissolved in resin, and electrons passing through its interior form a section image.

D. A mobile beam progressively excites the sample, and signals detected above the surface form the image.

Answer: (D)

Explanation

SEM uses a mobile beam to scan the specimen progressively and detects signals above the sample surface. Detecting electrons transmitted through a specimen after broad excitation is characteristic of TEM.

13. Which preparation sequence produces the replica used for scanning electron microscopy?

A. Cryofracture, surface sublimation, and shadowing with heavy ions such as platinum or silver.

B. Chemical staining, photon excitation, thick sectioning, and fluorescent labeling.

C. Fixation, dehydration, resin embedding, thin sectioning, and opacification.

D. Vacuum exposure, immunogold binding, resin removal, and transmitted-electron detection.

Answer: (A)

Explanation

SEM preparation uses cryofracture, surface sublimation, and heavy-ion shadowing to create a replica of the specimen. Resin embedding and thin sectioning belong to TEM preparation rather than SEM replica production.

14. What structural information can SEM reveal after a biological specimen is frozen and shadowed?

A. The localization of a protein within a thin resin section.

B. The three-dimensional structure of cells or macromolecules.

C. The internal passage of electrons through non-opacified regions.

D. The chemical identity of photons emitted by an illuminated specimen.

Answer: (B)

Explanation

Freezing and shadowing allow SEM to reveal the three-dimensional structure of cells or macromolecules. Protein localization by immunogold and electron transmission through thin sections are TEM-related outcomes.