Week 1 - observing the hidden world

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  • Created by: anannab
  • Created on: 07-05-21 16:16
What are the varieties of a light microscope?
Bright-field microscope
Dark-field microscope
Phase-contrast microscope
Fluorescence microscope
Confocal microscope
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How does a light microscope work?
Light microscopes use light to visualize an observe a specimen, light is refracted (bent) when passing from one medium to another, light microscopes exploit this to magnify an image
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What is a refractive index?
A measure of how greatly a substance slows the velocity of light
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How do you calculate magnification?
The total magnification is calculated by multiplying the magnification of the objective and ocular lenses (eyepiece)
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What is resolution?
The ability of a lens to distinguish two distinct points
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What is fixation? What are the two different types? How are they different?
To view your specimen you have to preserve its internal and external structure, and fix them into position.
Heat fixation: preserves overall morphology but not internal structures
Chemical fixation: protects fine cellular substructure and morphology
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What is staining?
Dyes makes internal and external structure of cell more visible by increasing contrast with background
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What are the two different ionized dyes?
Basic dyes = Have positively charged groups, bind to negatively charged molecules such as nucleic acids, many proteins, and the surfaces of bacterial and archaeal cells
Acidic dyes = In their ionized form, have a negative charge and bind to positively cha
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What is gram staining?
Divides bacteria into two groups, Gram-positive (stain purple) and Gram-negative (counterstained pink), based on the difference in the cell wall structure
It is an example of a differential stain
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What is a phase-contrast microscope?
Converts differences in refractive index/cell density into detected variations in light intensity
Some light rays from the hollow cone of light passing through unstained cell are slowed and become out of phase with the other light rays (dark against brig
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What is a fluorescence microscope?
Excitation with the light of a specific wavelength causes fluorochrome or fluorescent protein to emit longer-wavelength light
Shows a bright image resulting from the fluorescent light emitted by the specimen
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What is a confocal microscope?
Useful when looking at bacterial structures, particularly biofilms, it can look through the different layers
Confocal scanning laser microscopy (CSLM) creates sharp, composite 3D images of a specimen by using a laser beam, the computer is able to stack
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What is an electron microscope?
Electrons replace light as the ‘illuminating’ beam
The wavelength of the electron beam is much shorter than light, resulting in a much higher resolution.
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What are the two types of electron microscope?
Transmission electron microscope = Uses an electron gun with an electron magnet, to direct the beam onto the sample
Scanning electron microscope = Uses electrons excited from the surface of a specimen to create a detailed image, produces a realistic 3D i
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What is electron cryotomography?
Rapid freezing techniques provides a way to preserve the native state of structure examined in a vacuum
Images are recorded from many different directions to create 3D structures
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Other cards in this set

Card 2

Front

How does a light microscope work?

Back

Light microscopes use light to visualize an observe a specimen, light is refracted (bent) when passing from one medium to another, light microscopes exploit this to magnify an image

Card 3

Front

What is a refractive index?

Back

Preview of the front of card 3

Card 4

Front

How do you calculate magnification?

Back

Preview of the front of card 4

Card 5

Front

What is resolution?

Back

Preview of the front of card 5
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