Eating Habits - Lab Flashcards
Don’t place dirty slide in this beaker / tray.
cleaning solution
discarding contaminated materials
Remove all labels from tubes, placing them in appropriate racks on side of the room as shown
petri dishes with cultures
and contaminated swabs go in the biohazard bags
Dispose of used glass pipettes
in the discard pans on the side desk or placed on your desk. At the end before you leave lab, transfer all pipettes in one pan.
Don’t discard bulbs and pumps
in the pan
Before storing microscope back
replace the low objective lens into working position. The microscope is always stored with the lowest power objective lens locked in. Place plastic cover to avoid dust on the microscope
Condenser
focuses light on the specimen
- is a lens system located below the stage
- it doesn’t affect magnification
- may include mirrors and prism to deflect light
Iris diaphragm lever
adjust light intensity for best contrast
- is part of the condenser system, below the stage
Coarse knob
Coarse knob: allows for gross focusing
Fine focus knob
Fine focus knob: allows for fine tuning of the focus
Head
Head: supports the objective and ocular lens system
Ocular lens
lens in each eyepiece; lens closest to the eyes
provides additional 10 x magnification when used with objective lens
monocular vs binocular microscopes (?)
Objective lens
adjustable lenses on the revolving nosepiece
normally used to change magnification of a specimen
built to minimize distortion in specimen image / color
4 types of objective lenses on microscope (scanning, low, high and oil immersion)
Total magnification
times 10
Resolving power - aka resolution - (2)
refers to ability of lens to distinguish between 2 points, a specified distance apart
Resolution is dependent on
quality, specimen prep, numerical, wavelength, white light
quality and type of lenses the magnification
how the specimen has been prepared
numerical aperture of lens (i.e. ability of the lens to gather light)
- larger the numerical aperture, better resolution
wavelength (?) of the light source; can limit resolution at higher magnification
shorter the wavelength of light used, higher the resolution
white light used in compound microscope limits resolution of structures smaller than 0.2μm
Working Distance (your objective)
refers to the space between slide specimen and objective lens - higher the magnification, shorter is working distance
Usefulness of a microscope depends on degree…
of magnification and resolve
Light or bright field microscope
easy to use, can recognize cells but not finer details. cells lack contrast with water.
Contrast
difference in intensity between object and it’s background
100x objective lens - how it works (drown)
- oil displaces air, avoids refraction - oil increases numerical aperture (?), thus improves resolution
because more light rays are gathered into lens to produce image
Refraction
prevents light from entering the small opening of the high powered objective lens
Refractive index
is measure of the velocity of light as it passes through medium
Phase contrast
- contains special condenser to enhance contrast when viewing object - permits examination of internal structures- good for viewing objects without staining (as cilia and flagella)
Dark field
objects looks bright against dark background- contains special condenser with opaque disc to block light
- good for viewing motility of organisms and
- examining microbes that cannot be stained or they get distorted by staining procedures
Fluorescence microscope
normally use to visualize organisms that fluoresce
- often cells are treated with fluorescent dyes then observed for fluorescence
Electron microscope
uses electromagnetic lenses (?), electron and fluorscent screen to observe specimen instead of glass lenses and lightwavelength of electrons is approximately 1000x shorter than visible light
much higher resolution is obtained and greater detail can be observed.
Drawbacks to electron microscope
Lenses and processed specimen must be enclosed in a vacuum unit (air absorbs electron, expensive. Processing increases artifact chances and cannot be used to study living organisms
staining
contrast and light, internal and external structures, identification
provides contrast and increases resolution for light microscope- allows visualization with ease- reveals internal and external structures- aids in classification and identification
smear
smear thick - trouble seeing individual cells smear thin - you may find no organism too much stirring - disrupts cell arrangement
fixing (pipes)
adherence of microorganism to slide - accomplished by either heat or chemicals ( cold alcohol acetone mixture)
advantages of fixing
fixing inactivates the microorganisms- preserves major parts with minimum distortion - prevents specimen slipping in subsequent stain application and washing steps - makes subtle alterations so that organisms more readily accepts stains
mordant - purpose and what its made of
Fixes the dye. Iodine. an additive added to dye solution, to intensify the stain- it binds to the dye and makes it less soluble
advantages of mordant
like, coat, see
- it increases affinity of stain for biological specimen, stain is retained better- coats certain structures, so that it’s easier to visualize following staining
stains are made of what substance..
salts composed of positive and negative ion; only one part is colored. Chromophore: colored part of a stain
Basic (cationic) dye
positive part is colored - methalyne blue, crystal violet, malachite green
Acidic (anionic) dye (travel)
negative part is colored, sudan red, india ink
Simple stain
involves application of a single dye to a smear. highlights entire organism; shape and basic structures are visible, including arrangement of cells - are of relatively less value in diagnostic bacteriology
Differential stain
involves application of two or more dyes together or separately to a smear. mainly used to distinguish one group of bacteria from another- various dyes reacts with different bacterial structural components
Special stains - types FFN
FFN
3 types of special stains:
A. Negative stain (example: capsule stain) B. Flagellar stain C. Fluorescent stain
3 types of differential stain
gram, acid fast and spore stain
special stain
dye or color isolates specific structure of microbe.
negative stain uses what type of dye
on bacteria, uses anionic dyes. - chloroform.
bacteria is repelled by
acid. remains unstained.
halo around cell is…
negative acidic, likely the capsule
advantages of negative
get an idea of size and shape, and evidence of the capsule
what part gets stained in basic stain
the cell itself gets stained
chromatophores
part of plasma membrane. light reflecting cells.
euglena
looks like snap peas, has flagella. algae, eukaryote. bright green.
paramecium
dirty brown, eukaryote
stains (made of)
dyes, salt positive and negative ion
center of cheek stain dark part is
nucleus DNA
chromophore
positive part, blue part attracted to negative charge, DNA.
DNA negative part gets dyed due to
phosphate groups
gram negative color
pink and red
gram positive stains..(color)
peptioglycan, purple
decolorizing (nail polish +)
Alcohol/acetone. critical step. washes off stain. gram positive, water sucked out.
spore stain is a __stain
differential stain - can be positive or gram negative
gram positive rods..(ex)
make spores. only clostridium and bacillus anthracis.
use oil immersion lens with..
gram stain. no coverslip needed
acid-fast staining steps (car steam)
you’re mixing so it’s called mixed stain. primary dye - carbolfuscia dye on top of paper towel. heat with paper towel is fixing - steam acts as mordant. keep adding more carbonfuscia as you heat it. counterstain methalyne blue
real and virtual image
objective to real to ocular, ocular to virtual
The objective lens magnifies the specimen to produce real image that is projected to ocular lens . The real image is magnified by ocular lens to produce the virtual image.
virtual image is what position
upside down
stain used for cheek cell
alwasys simple stain, one dye
blue dye disassociates (eyes)
negative and positive. chromatophore is positive part, dye is attracted to negative part.
cheek cell is
eukaryotic cell
dark dots and rod shapes in cheek stain
are bacteria - prokaryotes
endspore stain is what type of stain
differential stain
advantages of gram staining
fast - gonnorhea, clues - strep pneumonia, treatment
it’s a fast and useful tool ex: urethral secretion (neissan gonorhea - only gram - diplococci) provides clues during the identification (lungs - strep pneumonia) for antimicrobial treatment (gram - like syphillis and TB can’t be treated)
disadvantages of gram staining
disease not distinct, can’t identify infection, stain poorly, need new cells
often, disease causing bacteria do not have distinct stain characteristics - the stain is not specific enough to diagnose the cause of most infection - some bacterial cells stain poorly or not at all; freshly grown bacteria is preferred. aged or old cells = misleading results