Microscopy Principles and Techniques Quiz

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Questions and Answers

What is the basic unit of length according to the text?

Nanometer (nm) (correct)

Micrometer (µm)

Millimeter (mm)

Angstrom (Å)

What is the magnification capability of an electron microscope compared to a light microscope?

1000x

In excess of 100,000x (correct)

100x

10x

What physical phenomenon causes the bending of light rays when they change medium?

Diffraction

Dispersion

Reflection

Refraction (correct)

What is the fraction equivalent of 10 nanometers (nm) in meters?

$10^{-9}$ meter Signup and view all the answers

What is the maximum magnification capability of electron microscopes?

Why are lenses and specimens in electron microscopes required to be in a vacuum?

To avoid interference from air molecules Signup and view all the answers

Which type of electron microscope is used to observe fine cell structure details?

Transmission Electron Microscope (TEM) Signup and view all the answers

What is the purpose of staining techniques in microscopy?

To improve contrast for observation Signup and view all the answers

What are basic dyes attracted to in staining techniques?

Negatively charged cellular components Signup and view all the answers

What is the most commonly used stain for distinguishing Gram-positive from Gram-negative bacteria?

Gram stain Signup and view all the answers

Which staining technique is used to detect organisms with high concentrations of mycolic acid in their cell walls?

Acid-fast stain Signup and view all the answers

What is the technique that uses fluorescent antibodies to tag specific proteins?

Immunofluorescence Signup and view all the answers

What is the purpose of differential staining?

To distinguish different types of bacteria Signup and view all the answers

Which staining technique involves one dye?

Simple staining Signup and view all the answers

What is the purpose of SEM in electron microscopy?

To observe surface details Signup and view all the answers

Why is staining necessary in microscopy?

Observing cells with a bright-field microscope is challenging due to their movement and transparency Signup and view all the answers

What are the shapes of cocci and rods (bacilli) bacteria?

Spherical and cylindrical Signup and view all the answers

What are examples of bacteria mentioned in the text?

Staphylococcus aureus and Salmonella typhimurium Signup and view all the answers

What is the function of the cytoplasmic membrane in bacteria?

Critical permeability barrier Signup and view all the answers

What types of molecules can pass through the cytoplasmic membrane without the need for transport proteins?

O2, CO2, N2, small hydrophobic molecules, and water Signup and view all the answers

What is the purpose of transport proteins in bacteria?

Function as selective gates for nutrient and waste transport Signup and view all the answers

Which type of transport system moves substances against a concentration gradient and requires energy?

Active transport Signup and view all the answers

What do bacteria use protein secretion systems for?

To actively move proteins out of the cell Signup and view all the answers

What distinguishes between gram-positive and gram-negative bacteria?

The composition of the cell wall Signup and view all the answers

What is the main component of the cell wall in bacteria?

Peptidoglycan Signup and view all the answers

What is the function of the cell wall in bacteria?

Prevents cell lysis Signup and view all the answers

What are the different types of bacterial groupings mentioned in the text?

Chains, diplococcus, clusters, and packets Signup and view all the answers

What are the sizes of vibrio, spirillum, and spirochete bacteria mentioned in the text?

7.5 µm to 15 µm Signup and view all the answers

What distinguishes major types of bacteria in the Gram stain?

Retention or loss of the dye Signup and view all the answers

What is the waxy coat produced by Mycobacterium that repels the Gram stain?

Acid-fast stain Signup and view all the answers

What is the main component of the rigid cell wall found only in bacteria?

Peptidoglycan Signup and view all the answers

What are the components of peptidoglycan?

N-acetylmuramic acid and N-acetylglucosamine Signup and view all the answers

How is the peptidoglycan cross-linked?

To create a large three-dimensional molecule Signup and view all the answers

What is unique to the cell wall subunit of bacteria?

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) Signup and view all the answers

What does the Gram-positive cell wall contain in addition to the thick peptidoglycan layer?

Teichoic acids Signup and view all the answers

What is the function of teichoic acids in the Gram-positive cell wall?

Functioning as a reservoir for cations and in cell wall construction Signup and view all the answers

What is the distinguishing feature of the Gram-negative cell envelope?

Thin peptidoglycan layer between two membranes Signup and view all the answers

What is the function of the outer membrane in the Gram-negative cell envelope?

Unique lipid bilayer embedded with protein Signup and view all the answers

What is the main function of the architecture of the bacterial cell envelope?

Distinguishing bacterial types and understanding their structure and function Signup and view all the answers

What does resolution refer to in microscopy?

The ability to see objects as distinct instead of a blur Signup and view all the answers

What is the function of immersion oil in bright-field microscopes with 100x lenses?

To displace air and prevent light from missing the objective lens Signup and view all the answers

What is the resolving power of electron microscopes compared to bright-field microscopes?

About 1,000-fold greater Signup and view all the answers

What is the purpose of dark-field microscopes in microscopy?

To create a bright image against a dark background by allowing only scattered light to enter the objective Signup and view all the answers

What is the limitation of the resolution of a light microscope?

Limited to 0.2μm due to the physical limitation of visible light Signup and view all the answers

What is the function of staining cells with dyes or electron-dense material in microscopy?

To improve contrast in microscopy Signup and view all the answers

What is the total magnification when using ocular (10x) and objective (40x) lenses in a compound microscope?

400x Signup and view all the answers

What does the refractive index measure in microscopy?

The relative speed of light as it passes through a medium Signup and view all the answers

What is the increase in the apparent size of an object compared to its actual size called in microscopy?

Magnification Signup and view all the answers

What is the ability to see objects against the background called in microscopy?

Contrast Signup and view all the answers

What is the limitation of the resolution of an electron microscope?

Limited to approximately 0.3 nm due to the shorter wavelength of electrons Signup and view all the answers

Study Notes

Microscopy Principles and Techniques

Refractive index measures the relative speed of light as it passes through a medium and is used by lenses to focus light.
Lenses use refraction to bend light and focus it based on the principles of refraction.
Magnification is the increase in the apparent size of an object compared to its actual size and is expressed as a ratio, e.g., "100,000x".
Resolution is the ability to see objects as distinct instead of a blur and is defined as the minimum distance at which two points can be distinguished as individuals.
Contrast is the ability to see objects against the background, and techniques like staining cells with dyes or electron-dense material can improve contrast in microscopy.
Bright-field microscopes are the most common in laboratories and use a series of magnifying lenses to evenly illuminate the entire field of view.
Compound microscopes have ocular (10x) and objective (4x, 10x, 40x, 100x) lenses, with the total magnification being the product of the magnifying power of both lenses.
The resolution of a light microscope is limited to 0.2µm due to the physical limitation of visible light, making it unable to see details of viruses.
Bright-field microscopes with 100x lenses require immersion oil to displace air and prevent light from missing the objective lens.
Dark-field microscopes direct light towards the specimen at an angle, allowing only scattered light to enter the objective and creating a bright image against a dark background.
Electron microscopes use electromagnetic lenses, electrons, and a fluorescent screen to replace glass lenses, visible light, and the eye, with a resolving power about 1,000-fold greater than bright-field microscopes.
The wavelength of electrons is about 1,000 times shorter than light, and the resolving power of electron microscopes is approximately 0.3 nm.

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Description

Test your knowledge of microscopy principles and techniques with this quiz. Explore topics such as refractive index, magnification, resolution, contrast, different types of microscopes, and the limitations and advantages of light and electron microscopy.