Chapter 2-Microscopy Flashcards
What is the size of the smallest viruses?
they are measured in nanometers (nm)
Microscopes produce _________ images
magnified
microscopes vary in _____________, ____________, & _______________.
illumination source, focusing method, specimen preparation
use visible light to illuminate specimens, can be simple or compound
light microscopy
objective magnification X ocular magnification
total magnification
the ability to distinguish two close adjacent objects as separate and distinct
resolution
what determines resolution?
wavelength of light used and the lenses used
specimens are visualized because of differences in contrast between specimen and surroundings, has a specific condenser lens, produces a dark image against a brighter background
bright-field microscope
distance between the front surface of lens and surface of cover glass or specimen when it is in sharp focus
working distance
uses a special condenser lens, image is formed by light reflected or refracted by specimen, bright image of the object against a dark background, observe a living, unstained preparation
dark-field microscope
converts slight differences in refractive index and cell density into easily detected variations in light intensity, used to observe living cells
phase-contrast microscope
used to visualize specimens that fluoresce after exposure of specimen to UV, violet, or blue light, some cells naturally fluoresce, shows a bright image of the object resulting from the fluorescent light emitted by the specimen, can locate specific proteins in cells
fluorescence microscope
creates image by detecting differences in refractive indices and thickness of different parts of specimen, excellent way to observe living cells
differential interference contrast microscope (DIC)
creates a sharp composite 3D image of specimens by using laser beam, aperture, to eliminate stray light, and computer interface
confocal microscopy
what are 2 types of slide preparations?
(1) unstained preparations
(2) stained preparations
why can is staining an effective mechanism for observing specimens?
stains improve contrast of the final image (specimen vs. surrounding)
kills microorganisms, preserves internal and external structures and adheres them to the slide
fixation
any distortion in the true morphology of the microorganism due to the technique itself
artifact (done through heat fixation or chemical fixation)
coloring ion
chromophore
chromophore cation, binds to cells and most dyes
basic dye
chromophore anion, repelled by cells and stains background
acidic dye
make internal and external structures of cell more visible by increasing contrast with background
dyes
simple staining techniques involve using __ dye and has few steps. all slides are stained in the same way
1 dye
differential staining techniques involve using ____ dyes and has several steps. Microorganisms are divided based on their staining properties (gram stain or acid-fast stain)
2 dyes
