Question 1

Which of the following best explains why the limit of resolution for a light microscope is approximately 0.2 μm?

Accepted Answer

Because the wavelength of visible light ranges from about 0.4 μm to 0.7 μm, and resolution is limited by the wavelength of the radiation used.

Question 2

A researcher wants to visualize the dynamic movement of mitochondria in living cells without fixing or staining them. Which microscopy technique should they use?

Accepted Answer

Phase-contrast or differential-interference-contrast microscopy

Question 3

Which of the following statements about fluorescence microscopy is CORRECT?

Accepted Answer

Fluorescence microscopy uses filters to select excitation and emission wavelengths, allowing specific detection of fluorescent dyes.

Question 4

A scientist is using immunofluorescence to detect a protein in a tissue section. They use a primary antibody against the protein and a fluorescently labeled secondary antibody. What is the main advantage of this indirect method?

Accepted Answer

It amplifies the signal because multiple secondary antibodies can bind to each primary antibody, increasing sensitivity.

Question 5

Which of the following best describes the principle of confocal microscopy?

Accepted Answer

It uses a pinhole to exclude out-of-focus light, allowing for optical sectioning and three-dimensional reconstruction.

Question 6

A researcher wants to localize a specific protein within the spindle pole body of yeast using electron microscopy. Which labeling technique should they use?

Accepted Answer

Immunogold electron microscopy with antibodies conjugated to colloidal gold

Question 7

Which of the following is a key advantage of using green fluorescent protein (GFP) as a tag in living cells?

Accepted Answer

GFP can be genetically fused to a protein of interest, allowing real-time visualization of protein dynamics in living cells.

Question 8

A scientist is studying the pathway of a newly synthesized protein from the ER to the Golgi apparatus. Which experimental approach would best allow them to track this process over time?

Accepted Answer

Pulse-chase labeling with a radioactive amino acid followed by autoradiography

Question 9

Which of the following best explains why electron microscopes can achieve much higher resolution than light microscopes?

Accepted Answer

Electrons have a much shorter wavelength than visible light, allowing for finer detail to be resolved.

Question 10

A researcher wants to introduce a membrane-impermeant fluorescent dye into a large population of cells without microinjection. Which method would be most effective?

Accepted Answer

Electroporation to transiently permeabilize the plasma membrane

Question 11

Which of the following best describes the process of 'caged' molecule activation in cell biology experiments?

Accepted Answer

A biologically active molecule is inactivated by a chemical group that can be removed by a flash of light, releasing the active molecule at a precise time and location.

Question 12

Which of the following is a limitation of using thin sections in transmission electron microscopy (TEM)?

Accepted Answer

Thin sections provide only two-dimensional projections, which can be misleading about the three-dimensional structure.

Question 13

Which of the following best describes the principle of negative staining in electron microscopy?

Accepted Answer

A heavy-metal stain surrounds the macromolecule, creating a negative image where the molecule appears lighter against a dark background.

Question 14

A scientist wants to measure rapid changes in intracellular Ca2+ concentration in different regions of a living neuron. Which technique would be most suitable?

Accepted Answer

Fluorescent Ca2+-sensitive indicator dyes imaged by fluorescence microscopy

Question 15

Which of the following is a key advantage of scanning electron microscopy (SEM) compared to transmission electron microscopy (TEM)?

Accepted Answer

SEM provides detailed three-dimensional images of specimen surfaces.

Question 16

Which of the following best describes the use of radioisotopes in pulse-chase experiments?

Accepted Answer

Radioisotopes are used to label molecules during a short pulse, and their fate is tracked over time after the pulse is replaced by nonradioactive molecules.

Question 17

Which of the following is TRUE regarding the use of antibodies in cell biology?

Accepted Answer

Antibodies can be labeled with fluorescent dyes or electron-dense particles to localize specific molecules in cells.

Question 18

Which of the following best explains why rapid freezing is used in specimen preparation for electron microscopy?

Accepted Answer

Rapid freezing preserves the native structure of biological molecules by preventing ice crystal formation and minimizing artifacts.

Question 19

A researcher is using fluorescence resonance energy transfer (FRET) to study protein-protein interactions. Which of the following is required for FRET to occur?

Accepted Answer

The emission spectrum of one fluorochrome must overlap with the absorption spectrum of the other, and the two proteins must be within about 2 nm of each other.

Visualizing Cells: Microscopy Techniques and Molecular Tools in Cell Biology

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