1.3 Microscopy Flashcards
What is magnification?
the ability of a lens to enlarge the image of an object when compared to the real object.
What is resolution?
ability to tell that two separate points or objects are separate.
What is contrast?
contrast—visible differences between the parts of a specimen
Describe the relationship between resolution and the wavelength of light.
Resolution allows for us to tell that two seperate objects or points are seperate. Wavelengths allows for us to distinguish between separate things. Shorter wavelengths allow for us to see smaller things.
Brightfield microscope (Light microscope)
is a compound microscope with two or more lenses that produce a dark image on a bright background. (most common)
Darkfield microscope (Light microscope)
is a brightfield microscope that has a small but significant modification to the condenser. resulting image typically shows bright objects on a dark background
Phase-contrast microscope (Light microscope)
use refraction and interference caused by structures in a specimen to create high-contrast, high-resolution images without staining. It is the oldest and simplest type of microscope that creates an image by altering the wavelengths of light rays passing through the specimen.
Differential Interference Contrast microscope (Light microscope)
results in high-contrast images of living organisms with a three-dimensional appearance.
Fluorescence microscope (Light microscope)
uses fluorescent chromophores called fluorochromes, which are capable of absorbing energy from a light source and then emitting this energy as visible light. Fluorochromes include naturally fluorescent substances (such as chlorophylls) as well as fluorescent stains that are added to the specimen to create contrast.
Confocal microscope (Light microscope)
uses a laser to scan multiple z-planes successively. This produces numerous two-dimensional, high-resolution images at various depths, which can be constructed into a three-dimensional image by a computer.
Two Photon microscope (Light microscope)
which uses a scanning technique, fluorochromes, and long-wavelength light (such as infrared) to visualize specimens.two-photon microscope useful for examining living cells within intact tissues—brain slices, embryos, whole organs, and even entire animals.
Transmission electron microscope (Electron Microscopes)
it uses an electron beam from above the specimen that is focused using a magnetic lens (rather than a glass lens) and projected through the specimen onto a detector. Electrons pass through the specimen, and then the detector captures the image
Scanning Probe Microscopes
does not use light or electrons, but rather very sharp probes that are passed over the surface of the specimen and interact with it directly. This produces information that can be assembled into images with magnifications up to 100,000,000⨯. Such large magnifications can be used to observe individual atoms on surfaces. To date, these techniques have been used primarily for research rather than for diagnostics.
Fixation
The “fixing” of a sample refers to the process of attaching cells to a slide. Fixation is often achieved either by heating (heat fixing) or chemically treating the specimen. In addition to attaching the specimen to the slide, fixation also kills microorganisms in the specimen, stopping their movement and metabolism while preserving the integrity of their cellular components for observation.
Basic dyes are for?
basic dyes such as basic fuchsin, crystal violet, malachite green, methylene blue, and safranin typically serve as positive stains.
Acidic dyes are for?
the negatively charged chromophores in acidic dyes are repelled by negatively charged cell walls, making them negative stains. Commonly used acidic dyes include acid fuchsin, eosin, and rose bengal.
Gram stain. Identify the reagents used and describe the appearance of the two
types of bacterial cells after each step in the staining process.
Crystal violet, Iodine, Alcohol, Safranin
- They both stay purple during first two steps, then gram negative turns colorless during step 3 (alcohol) and it turns pink and red. Gram positive stays purple the whole time.
How do Endospore stains look?
uses heat to push the primary stain (malachite green) into the endospore. Washing with water decolorizes the cell, but the endospore retains the green stain. The cell is then counterstained pink with safranin. The resulting image reveals the shape and location of endospores, if they are present. The green endospores will appear either within the pink vegetative cells or as separate from the pink cells altogether. If no endospores are present, then only the pink vegetative cells will be visible (
How do Capsule stains look?
Capsules do not absorb most basic dyes; The dye stains the background but does not penetrate the capsules, which appear like halos around the borders of the cell.
How do Flagella stain look?
Staining to help us see the flagella
