Term
| Light path in compound light microscope |
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Definition
| Light source -> Condenser focuses light on specimen -> Light from specimen is focused by objective lens then eyepiece lens |
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Term
| Light vs. Electron Microscopy (Magnification, resolving power, specimens, stains, cytochemistry, 3D studies) |
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Definition
- Magnification: 2,500x (Light) vs. 300,000x (Electron)
- Resolving power: .2 microns (Light) vs. .1 nm (Electron)
- Specimens: Living or fixed (Light) vs. fixed (Electron)
- Stains: Dyes or fluorescence (Light) vs. Heavy metals (Electron)
- Cytochemistry: both show enzyme digestion and autoradiography. Antibodies linked to fluorescent probe (Light) or heavy metal (Electron)
- 3D sections: Confocal optical serial sections (Light) vs Serial sections (Electron) |
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Term
| What do inhibitors do? Give examples. |
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Definition
Inhibitors are specific, inhibit only one cell component, may be reversible. Inhibitors allow scientists to examine cultured cells.
- Vinblastine and Vincristine disassemble microtubules.
- Cytochalasin disassembles actin filaments |
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Term
| 4 types of light microscopy |
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Definition
1) Bright-field microscopy - little detail unless stained (stain allows one light wavelength to permeate cell).
2) Phase-contrast microscopy - useful for ordered structure (mitotic spindles and striated muscle)
3) Nomarski differential-interference-contrast microscopy - gives 3D appearance (light waves enter cell in phase, leave out of phase)
4) Dark-field microscopy - cell illuminated from the side, scattered light seen against dark background |
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Term
| How does fluorescent microscopy work? |
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Definition
- Fluorescent molecules are excited by one light wavelength and emit another.
- First filter only allows specific wavelength to reach specimen, second filter allows different wavelength to reach observer. Filters are specific for a particular fluorescence.
- Two or more fluorescent dyes can be used by going back and forth between filters. |
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Term
| What is confocal microscopy? What are its benefits? |
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Definition
Confocal: excludes out-of-focus light at detector, avoids blurring
The illuminating laser light scans the field in the same plane of focus, information is integrated into image.
Successive optical sections can be integrated to give 3D image. |
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Term
| Explain how antibodies can be used to identify specific molecules. |
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Definition
- Fluorescent molecules can be linked to an antibody then bound to specific molecule. The amount of fluorescence can be increased by binding markers to secondary antibodies (which bind to primary antibodies).
Electron-dense structures (i.e.- gold) can also be linked to an antibody which then binds to a specific molecule. Seen in TEM. |
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Term
| How does a scanning electron microscope (SEM) work? |
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Definition
- 3-D image, magnification and resolution intermediate between Light microscope (LM) and Transmission Electron microscope (TEM)
- Specimen is fixed with buffer, dehydrated, coated with heavy metal.
- Electron gun shoots narrow beam of electrons, electrons scattered by specimen gathered by detector. |
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Term
| What does cytochemistry do? |
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Definition
Enables identification of specific molecules by LM and TEM
- LM: fluorescent dyes stains
- TEM: heavy metals (ex: cytochemical reaction with lead phosphate indicates presence of acid phosphatase, defining enzyme for lysosomes) |
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Term
| Genetic techniques in cell biology |
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Definition
- Study mutants
- Mutations can be induced by radiation or chemicals
Because many genes are conserved, data about one gene in an organism is often applicable to related organisms |
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Term
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Definition
GFP = Green fluorescent protein
- GFP can be combined with gene for protein through recombinant DNA techniques.
Chimerical gene codes for the protein, can be visualized through fluorescent microscopy |
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