Lab Exam Flashcards
Stage
Fixed platform with an opening in the center allowing for passage of light from illuminating source to lens system
Mechanical stage
Can be moved vertically or horizontally by means of adjustment controls.
Illumination
Light source positioned in the base of the instrument
condenser
Component directly under the stage contains two sets of lenses that collect and concentrate light
Iris diaphragm
Shutter controlled by a lever that is used to regulate the amount of light entering the lens system
Body tube
Above the stage, attached to the arm of th microscope’
Ocular lens
Eyepiece lens
Nosepiece
Moveable, contains objective lens
Coarse adjustment and fine adjustment knobs
Below stage
Magnification
Enlargement of a specimen using a two lens system: ocular and objective
Objective produces what kind of image?
Real image
Ocular lens produces the
Final image
Resolving power
How far apart two adjacent objects must be before a given lens shows them as discrete entities. When two objects look as one, the resolution has been lost
Numerical aperture
Function of the diameter of the objective lens in relation to its focal length. RP=wavelength of light/2x numerical aperture
refractive index
The bending power of light passing through air from the glass slide to the objective lens
As the magnification of the lens increases,
The working distance decreases and the numerical aperture of the objective lens increases
Parfocal
When one lens is in focus, others will also have the same focal length
Heat fixation
Rapid movement of specimen over flame fixing to the slide
Sub culturing
Transfer of organism from one medium to another
Pure culture
Containing only one specimen
Uniform fine turbidity
Finely dispersed growth throughout
Flocculent
Flakey aggregates dispersed throughout
Pellicle
Thick pad like growth on surface
Sediment
Concentration of growth at the bottom of broth culture may granular, flaky or flocculent
Crateriform
Liquefied surface is saucer-shaped
Stratiform
Complete liquefaction of the upper half of the medium
Simple staining
Stained with single reagent: methylene blue, crystal violet and carbon fuchsin
Diplo
Pair
Strepto
Chain
Staphlyo
Cluster
Tetrad
4
Sarcina
Packet of 8
Vibrios
Curved rod
Spirilla
Helical and rigid
Spirochetes
Helical and flexible
Negative staining
Requires use of acidic stain - cells remain discernible to the background
Differential Staining
Use of at least four chemical reagents
Primary stain
Impart color to cells
Crystal Violet
Secondary stain
Intensifies color
Gram’s iodine
Third stain
Decolorizing agent
Alcohol
Counterstain
Fourth stain; has contrasting color to the primary stains
Safranin
Gram +
Purple
Gram -
Red
The best gram stains are made with cultures that are
Less than 24 hours old
Types of acidic dyes
Sodium eosinate
India ink
Nigrasine
Negative stain
Indirect stain that colors the background due to polarization of ions in cell coat and pigment
Color is in the negative ion
Positive stain
Color is in the positive ion…. basic dyes
False gram reaction
Looks one way but is actually another
False gram+
Smear is too think
Specimen was not fully decolorized
False gram -
Over decolorized
Over heat fixed
Bacteria older than 24 hours
Micrococcus luteus
Gram +
Cocci in tetrads
Yellow colonies on agar plate
Escherichia coli
Bacillus
No cell arrangement
Gram -
White colonies
Serratia marcescens
Gram -
Bacillus no arrangement
Pink red colonies at 25 degrees celsius
White colonies at 37 degrees
Difference in color indicates activity of the pigment gene due to temperature differences
Advantages of hanging drop
Can observe life processes such as motility, cell division, phagocytosis,
Distortion of cells
Observation of cells that stain poorly or not at all
Advantages of acidic dyes
No distortion of cells since there is no heat fixing of the slide
Can observe orgs that stain poorly or not at all
True motility
Has directional movement with purpose
Brownian movement
Stationary bouncing caused by random collisions
