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Microbio Ch. 3
Test 1
| Question | Answer |
|---|---|
| Focal Point | focuses light rays at a specific place |
| Focal length | distance between center of lens and focal point |
| Strength of lens | related to focal length |
| Refraction | light bends when passing from one medium to another |
| Refractive index | measure of light bending ability |
| Purpose of Immersion oil | same refractive index as glass so ligth will not bend any further. |
| white light | long wave length & cannot resolve structures less than 0.2 um |
| Numerical aperture | function of the diameter of the objective lens in relation to its focal length |
| Light Microscope | uses visible light to observe specimen; 2 lenses |
| Bright Field | 2 lens, specimen is dark ; bright background; best for non viable stained preps |
| Darkfield | best for living organisms; condenser blocks light from directly entering the objective lens |
| Phase-Contrast | no staining required, study living organisms. Dark against light backgrounnd |
| Fluorescence | use fluorochromes dyes. UV rays. Best for ABs. |
| Electron | best for objects smaller than 0.2um like viruses and cell structures |
| types of electron microscope | Transition and Scannin |
| TEM | uses transmitted electrons to produce an image; light passes through specimen. can be viewed through an eyepiece |
| SEM | only able to see the surface, uses elcetrons reflected from the surface of a specimen to creat image. can only be viewed through a viewing screen |
| Smear | dried preparation of bacterial cells on a glass slide |
| Heat Fixation | smear is fixed on slide to prevent washin away. coagulates bacterial protein, kills microbes |
| Stain (chemical) | organic compound containing a benzene ring + a chromophore(color) and auxochrome(charge) group |
| basic dye | positive ions |
| acidic dye | negative ions |
| types of basic dyes | crystal violet, methylene blue, malachite green,safranin |
| types of acidic dyes | acid fuchsin, eosin, nigrosin |
| Negative staining | used to observe the overall shape size and capsules |
| types of staining | simple, differential, special |
| Simple staining | using 1 dye |
| differential staining | at least 3 chemical reagents |
| Mordant | helps a dye bond more w/ the surface of the cell |
| Differential staining steps | Primary stain, decolorizing agent, counterstain |
| Primary stain | stains entire cell |
| Decolorizer | removes primary stain from certain parts of cells |
| counterstain | contrasting color |
| Hans Christian Gram | developed differential staining procedure |
| gram staining | classifies bacteria into 2 groups |
| gram staining procedure | primary stain(crystal violet), apply iodine, apply alcohol(most important), counterstain(safranin) |
| gram positive bacterial wall | thicker layer of peptidoglycan |
| gram negative bacterial wall | thinner layer of peptidoglycan + layer of LPS as part of cell. remain colorless until counterstained |
| Beta Lactams | more active against gram positive bacteria and less against gram negative as they can't penetrate LPS |
| Acid-Fast Staining uses | used to distinguish Mycobacterium and Nocardia |
| Acid-fast stain | binds strongly to a waxy material in cell wall |
| Acid-Fast staining procedure | carbol fuchsin, wash with acid alcohol, counterstain with methylene blue |
| Special Stains | used to color specific parts of microorganisms |
| Special staining uses | highlights endospores, flagella, capsules |
| Endopore Staining | malachite green, wash, counterstain with safranin |
| Capsule staining | India Ink or nigrosin is used to stain background dark then perform simple stain |
| Flagella Staining | mordant is used to build up diameter then stain with carbol fuchsin it becomes visible under the light microscope |
Created by:
nani012506
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