29 terms

exercise 3, 4, 5, 6

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acidic dyes
anions (neg) that combine with cations of a base in the stained cell to form a salt.
basic dyes
posses cations that combine with an acid the stained material to form a salt
neutral stains
are made by combining acidic and basic dyes. they are most useful for staining complex cells of higher forms because they permit differentiation of interior structures, some of which are basic, some acidic.
basophilic
cells and structures that stain with basic dyes are said to be
acidophilic
those that stain with acid dyes are termed
spherical, rod, spiraled
the three basic shapes of bacteria
coccus
a round bacterium is called
bacilli
a rod-shaped organism
spirillum
a spiraled bacterium with at least two or three curves in its body is called a
spirochetes
long sinuous organisms with many loose or tight coils
diplococci
cocci occurs in pairs
streptococci
chains of cocci
staphylococci
clusters of coccie
tetrads
packets of four
diplobacilli
bacilli in pairs
streptobacilli
chains of bacilli
palisade
bacilli line up in bundles of parallel bacilli, others may form V, X, Y.
pleomorphism
show great variation in their size and length
Why are specimens to be stained suspended in sterile saline or distilled water?
we use sterile water because to avoid false result by microorganism having in the water and same reason for distilled also to avoid impurities like crystals of some metal ions and also to avoid other microorganisms
for what reason do we need to stain bacteria
to view them easier and clearly, to have contrast in order to identify cell morphology of the bacteria.
crystal violet
The first group retains the color of the primary dye and it is called the gram postive
safranin
counterstain
acetone alcohol
decolorizing agent
iodine
mordant, a chemical that fixes a dye in or on a substance by combining with dye to form an insoluble compound.
gram positive cell wall
are composed of thick, tightly linked peptidoglycans(protein sugar complexes) in which the crystal violet-iodine complex becomes trapped, thereby enabling the cells to resist decolorization.
gram negative cell wall
have high concentration of lipids in their outer membranes that it makes it easier for the decolorizer to dissolve the lipids.
what is the function of the iodine solution in the Gram stain? if it were omitted, how would staining results be affected
to fix the dye on the slide in order to form insoluble substance. and if it is ommitted then, when flushed with water and the alcohol decolorized, the bacteria will come off.
what is the purpose of the alcohol solution in the Gram Stain?
for the colors to show either purple (gram +) or gram (-) and to fix the colors.
what counterstain is used? why is it necessary?
safranin, because it helps show the gram- bacterias