Microscope Techniques and Cell Biology - Laboratory Exercise 3
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A set of practice Q&A flashcards covering cell types, microscope types, components, operation, measurements, and drawing guidelines based on Laboratory Exercise 3 notes.
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What are the two major cell types distinguished by the location of chromosomes?
Prokaryotic cells and eukaryotic cells.
What is the defining feature of prokaryotic cells?
They lack a nucleus and membrane-bound organelles; DNA is located in the nucleoid without a surrounding membrane.
Which organisms are prokaryotes?
Bacteria and archaea (Archaebacteria).
Which organisms are eukaryotes?
Fungi, protozoa, plants, and animals.
What is the basic function of a microscope?
To magnify an image so that we can visualize cellular and subcellular details.
How does a light microscope operate?
Visible light passes through the specimen and lenses to magnify the image projected to the eye, film, or screen.
What is the purpose of a phase contrast microscope?
To examine unstained living cells and tissues by exploiting refractive index differences to produce high-contrast images.
How does phase contrast achieve high contrast?
By using induced phase shifts with rings in the condenser and objective to reduce deflected light, making dense areas appear darker.
What is the use of a dark-field microscope?
To observe transparent specimens on a dark background; only light scattered by structures reaches the objective.
Why can't dark-field microscopy surpass bright-field in resolution?
Because it uses the same wavelength light as bright-field.
What does a fluorescence microscope study and how does it work?
Fluorescent structures by exciting them with UV light and detecting emitted visible light through filters.
What does a polarized microscope detect?
Birefringent (double-refracting) structures by rotating the plane of polarized light.
What is electron microscopy (EM) and its key advantage?
An imaging method using electrons instead of light, yielding much shorter wavelengths and higher resolution (~0.002 nm).
What are the two main types of electron microscopes and their focus areas?
SEM (scans the surface/topography) and TEM (transmits through thin sections to reveal internal ultrastructure).
What is resolving power?
The ability of a microscope lens to produce separate images of closely spaced objects.
What is the typical naked-eye resolving limit?
About 0.2 mm.
How is total magnification calculated?
Total magnification = magnification of objective × magnification of ocular.
What is the typical ocular magnification?
10×.
What are the common objective lenses on a compound microscope?
4× (low power), 10× (medium power), 40× (high power), and often 100× (oil immersion).
What does numerical aperture (NA) affect?
Higher NA increases resolving power and useful magnification.
What is the working distance?
The space between the objective lens and the slide; it decreases as objective power increases.
What is the field of view?
The circle of light seen through the ocular.
What is the vernier scale on the mechanical stage used for?
To read precise stage positions (X-Y); example reading can be 19.6 mm.
What is the function of the rheostat on a microscope?
To vary the intensity of the light source.
What do the condenser and iris diaphragm do in a light microscope?
Condenser focuses light on the specimen; iris diaphragm controls brightness and contrast.
What is the purpose of a wet mount in Exercise 2?
To observe living unicellular organisms and, later, multicellular organisms in water.
Which organisms are used for wet mounts in Exercise 2?
Paramecium (unicellular); cyanobacteria, spirogyra, protozoa; plant cells (scallion/green onion) and animal cheek cells.
What are common plant and animal cells observed in Exercise 2?
Plant cells: scallion/green onion leaves; Animal cells: cheek epithelial cells.
What are the main organelles you should be able to identify in observed cells?
Nucleus, plasma membrane, cell wall (in plants), and other organelles.
What is a contractile vacuole and which organism is it associated with here?
An organelle involved in osmoregulation; observed in Paramecium.
What is Spirogyra sp. used to illustrate at 400× magnification?
Visible features such as cell wall and chloroplasts in a filamentous alga.
What are the key guidelines in Lab Drawings Appendix 1?
Drawings should be large, centered, with a descriptive title including lens power; include scale and labels; use pencil; avoid shading; accurate and focused representation.
What should the title of a lab drawing include?
The title, the scientific name (italicized or underlined), and the lens power used, e.g., drawn as seen through 400× magnification.
What are the two major cell types distinguished by the location of chromosomes?
Prokaryotic cells and eukaryotic cells.
What is the defining feature of prokaryotic cells?
They lack a nucleus and membrane-bound organelles; DNA is located in the nucleoid without a surrounding membrane.
Which organisms are prokaryotes?
Bacteria and archaea (Archaebacteria).
Which organisms are eukaryotes?
Fungi, protozoa, plants, and animals.
What is the basic function of a microscope?
To magnify an image so that we can visualize cellular and subcellular details.
How does a light microscope operate?
Visible light passes through the specimen and lenses to magnify the image projected to the eye, film, or screen.
What is the purpose of a phase contrast microscope?
To examine unstained living cells and tissues by exploiting refractive index differences to produce high-contrast images.
How does phase contrast achieve high contrast?
By using induced phase shifts with rings in the condenser and objective to reduce deflected light, making dense areas appear darker.
What is the use of a dark-field microscope?
To observe transparent specimens on a dark background; only light scattered by structures reaches the objective.
Why can't dark-field microscopy surpass bright-field in resolution?
Because it uses the same wavelength light as bright-field.
What does a fluorescence microscope study and how does it work?
Fluorescent structures by exciting them with UV light and detecting emitted visible light through filters.
What does a polarized microscope detect?
Birefringent (double-refracting) structures by rotating the plane of polarized light.
What is electron microscopy (EM) and its key advantage?
An imaging method using electrons instead of light, yielding much shorter wavelengths and higher resolution (~~~~0.002 nm).
What are the two main types of electron microscopes and their focus areas?
SEM (scans the surface/topography) and TEM (transmits through thin sections to reveal internal ultrastructure).
What is resolving power?
The ability of a microscope lens to produce separate images of closely spaced objects.
What is the typical naked-eye resolving limit?
About 0.2 mm.
How is total magnification calculated?
Total magnification = magnification of objective
magnification of ocular.
What is the typical ocular magnification?
10
.
What are the common objective lenses on a compound microscope?
4
(low power), 10
(medium power), 40
(high power), and often 100
(oil immersion).
What does numerical aperture (NA) affect?
Higher NA increases resolving power and useful magnification.
What is the working distance?
The space between the objective lens and the slide; it decreases as objective power increases.
What is the field of view?
The circle of light seen through the ocular.
What is the vernier scale on the mechanical stage used for?
To read precise stage positions (X-Y); example reading can be 19.6 mm.
What is the function of the rheostat on a microscope?
To vary the intensity of the light source.
What do the condenser and iris diaphragm do in a light microscope?
Condenser focuses light on the specimen; iris diaphragm controls brightness and contrast.
What is the purpose of a wet mount in Exercise 2?
To observe living unicellular organisms and, later, multicellular organisms in water.
Which organisms are used for wet mounts in Exercise 2?
Paramecium (unicellular); cyanobacteria, spirogyra, protozoa; plant cells (scallion/green onion) and animal cheek cells.
What are common plant and animal cells observed in Exercise 2?
Plant cells: scallion/green onion leaves; Animal cells: cheek epithelial cells.
What are the main organelles you should be able to identify in observed cells?
Nucleus, plasma membrane, cell wall (in plants), and other organelles.
What is a contractile vacuole and which organism is it associated with here?
An organelle involved in osmoregulation; observed in Paramecium.
What is Spirogyra sp. used to illustrate at 400
magnification?
Visible features such as cell wall and chloroplasts in a filamentous alga.
What are the key guidelines in Lab Drawings Appendix 1?
Drawings should be large, centered, with a descriptive title including lens power; include scale and labels; use pencil; avoid shading; accurate and focused representation.
What should the title of a lab drawing include?
The title, the scientific name (italicized or underlined), and the lens power used, e.g., drawn as seen through 400
magnification.
What is the nucleoid region in prokaryotic cells?
It is the area where the DNA is located, but unlike a eukaryotic nucleus, it lacks a surrounding membrane.
What does ultrastructure refer to in microscopy?
It refers to the fine internal details of cells or tissues that can only be revealed using high-resolution methods like Transmission Electron Microscopy (TEM).
What is the role of the ocular lens in a microscope?
Also known as the eyepiece, it is the lens through which you look, typically providing a 10\times magnification that is multiplied by the objective lens magnification to calculate total magnification.
What is the role of the objective lens in a microscope?
These are the lenses positioned directly above the specimen, available in various magnifications (e.g., 4\times, 10\times, 40\times, 100\times). Their magnification is combined with the ocular lens for total magnification.
Explain oil immersion in microscopy.
This technique involves placing a drop of immersion oil between the 100\times objective lens and the slide. The oil reduces light refraction, increasing the numerical aperture and thus the resolution and clarity of the image.
What does it mean for a structure to be birefringent?
A birefringent structure has the property of double refraction, meaning it splits incident polarized light into two rays. This property is detectable with a polarized microscope.