| Question |
Answer |
| Micrometer |
10^-6 m |
| prefix micro |
Means unit following should be divided by 1 million |
| nanometer (nm) |
10^-9 m |
| Quorum |
Ability of bacteria to communicate & coordinate behavior - group comes together, secrete "inducer" that changes behavior. |
| In compound microscope, light rays from an __ pass through a __ that has lenses to direct rays. |
illuminator, condenser |
| Lenses closest to specimen |
objective lenses |
| eyepiece |
occular lenses |
| How is total magnification of compound light microscope calculated? |
Objective lense magnification (power) times the ocular lense magnification (power). |
| Resolution |
Resolving power - ability of lenses to distinguish fine detail & structure - distinguish 2 points a specific distance apart. |
| The __ the wavelength of light, the greater the resolution. |
shorter |
| The white light in compound light microscope has __ wavelength. |
long - cannot resolve smaller than 0.2 micrometer |
| Max magnification of compound light microscope. |
2000x |
| Refractive index |
Measure of light-bending ability of a medium. |
| How do you change refractive index of specimens? |
By staining them - they will then have different refractive indexes. |
| Immersion oil has same __ as glass. |
refractive index - keeps light rays from refracting as they enter air - increases resolving power of lenses. |
| Brightfield illumination |
Uses visible light for illumination - white background. |
| Darkfield microscope |
Used for invisible microorganisms & cannot be stained - uses darfkield condenser with opaque disk - sees only reflected light - black background. |
| Phase-contrast microscope |
Good to examine interior cell structures - Used with living microorganisms - don't have to fix them - uses special condenser to absorb refracted light & interference patterns. |
| Differential interference contrast (DIC) microscopy |
Measures differences in refractive indexes - 2 beams of light split by prisms & add contrasting colors - higher resolution - 3D. |
| Fluorescense |
Ability of substances to absorb short wavelengths (ultraviolet) & give off longer length (visible) - glowing |
| Fluorescence microscopy |
Organism stained with dye to glow (fluorochromes) & viewed under ultraviolet light against dark background. |
| Principal use of fluorescence microscopy |
FA - fluorescent - antibody technique/immunoflorescence - can detect bacteria, etc w/in cells by viewing if specific antibodies attach. |
| Confocal microscopy |
3D image made by light microscope - uses fluorescent stains & laser - computer constructs image from stack of images - ATP & Ca ion concentrations. |
| Scanning Acoustic Microscopy (SAM) |
Evaluates sound waves sent through specimin - used to study living cells attached to another surface - cancer cells, artery plaque, & biofilms. |
| What feature of confocal microscopy eliminates blurring? |
Use of pinhole aperture |
| Principal use of SAM |
Study living cells attached to another surface - cancer, plaque, etc. |
| Images produced by electron microscope are always __. |
in black & white |
| 2 types of electron microscope. |
Transmission - thin sections of a specimen & scanned - 3d view of surface. |
| Positive staining |
Salts of various heavy metals used as stains & fixed onto specimens. |
| Negative staining |
Increase electron opacity of surrounding field & useful when studying very small particles/specimins like virus particles, bacterial flagella, proteins. |
| Shadow casting |
Heavy metals adhere at 45 degree angle on one side & leaves a shadow to crate 3d for size. |
| TEM has __ resolutions & valuable for examining __ of specimen. |
high - layers |
| Drawback of TEM? |
Only thin specimens - kills specimen & causes shrinking & distortion - artifacts. |
| Scanning Electron Microscope (SEM) |
3d view of surface - good for intact cells & viruses - uses electrons |
| Scanned-probe microscopes |
Doesn't modify specimen or damage it - map atomic & molecular shapes, characterize magnetic & chemical properties, & temp variation inside cells. |
| Scanning tunneling microscopy (STM) |
Thin metal (tungsten) probe scans specimen & produces an image revealing bumps & depressions of the atoms on surface of specimen. |
| Atomic Force Microscopy (AFM) |
Metal & diamond probe - 3d image - doesn't damage specimen - both biological substances & molecular processes. |
| Stains are __ composed of positive & negative ion. |
salts |
| The color of __ dyes is in the positive ion. |
basic |
| The color of __ dyes is in the negative ion. |
acidic |
| Name some basic dyes |
crystal violet, methylene blue, malachite green & safranin |
| Most commonly used dyes |
Basic dyes - methylene blue |
| __ dyes are not attracted to most types of bacteria. |
Acidic - repelled by negatively charged bacterial surface. |
| Negative staining is used when for bacteria? |
To prepare colorless bacteria against colored background - eosin, acid fuchsin, & nigrosin |
| Simple stain |
Aqueous or alcohol solution of single basic dye. |
| Mordant |
Chemical that increases affinity of stain for biospecimen or coats it. |
| Differential stains |
React differently with different bacteria & used to identify - gram stain & acid-fast stain. |
| Gram stain |
Stain that classifies bacteria into gram-positive & gram negative. |
| 4 steps of gram staining |
(1) basic purple dye (primary) applied, (2) dye washed off & mordant applied, (3) alcohol-acetone solution (decolorized), (4) basic red dye applied. |
| Primary stain |
Basic purple dye (crystal violet) |
| Decolorizing agent |
Alcohol/acetone solution to remove purple from some cells. |
| Gram-positive |
Bacteria retaining color of purple dye & iodine after decolorization. |
| Gram-negative |
Lose dark violet color after decolorization. |
| Counterstains |
Basic dye safrain that turn gram-negative bacteria pink - doesn't affect gram-positive. |
| What reacts to create gram stain? |
Structural differences in cell wall - gram-positive have thicker peptidoglycan cell wall, gram-negative have lipopolysaccharides in cell wall. |
| Gram-___ bacteria tend to be killed by penicillins & cephaliosporins. |
positive |
| Acid-fast stain |
Binds to bacteria with waxy material in cell walls - mycobacterium tuberculosis & leprosy. |
| What diseases can be diagnosed using acid-fast stain? |
Tuberculosis & leprosy |
| Special stains |
Used to color & isolate special parts of microorganisms & to find capsules. |
| Capsule |
Gelatinous covering - determines organism's virulence |
| Virulence |
Degree to which pathogen can cause disease. |
| Endospore |
Cannot be stained by ordinary methods - resistant structure formed inside same bacteria which protects it from adverse environment. |
mr. charles11
