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Mcb 101 - Exam 1 (Loncapa) Questions And Answers With Verified Solutions Already Passed!!!
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Mcb 101 - Exam 1 (Loncapa) QuestionsAnd Answers With Verified Solutions
Already Passed!!!
Immersion oil is only used with which objective: - ANSWER✔✔ 100x
To determine the total magnification of a compound microscope: - ANSWER✔✔
take the product of the magnifications of the lens near the specimen and the lens
near your eye
When you heat-fix a slide you should: - ANSWER✔✔ pass the back side of the
slide quickly through a flame 2 or 3 times
Which stain will be used to stain the bacterial cells for the simple stain
experiment? - ANSWER✔✔ Crystal violet
When making a bacterial smear of the broth culture you should: - ANSWER✔✔
not add a drop of water to the slide
In order to switch from one objective to another on the brightfield microscope
you should: - ANSWER✔✔ rotate the black knurled nosepiece
When should you pass your slide through a flame? - ANSWER✔✔ You should pass
the slide through a flame before preparing the smear and once the smear dries
When dry your bacterial smear should look: - ANSWER✔✔ like a light haze
,When making a Gram stain, you cover the smear completely with iodine and let
sit for how long? - ANSWER✔✔ 1 minute
Put the following steps for performing a Gram stain in order (number 1 should be
the first step):
Blot the slide carefully with bibulous paper until dry.
Heat-fix the slide by passing it quickly through the flame of a micro burner 2 or 3
times.
Hold the slide at a 45o angle over the sink and allow drops of ethanol to flow over
the smear. Rinse gently with water.
Cover the slide with iodine and let sit for the alotted time. Pour off the iodine and
rinse gently with water.
Spread your bacterial sample on the slide, using an inoculating loop, in an area
about the size of a quarter. Allow the smear to dry.
Pass one side of a clean slide through a micro burner to remove dust.
Cover the smear with safranin and let sit for the alotted time. Pour off the
safranin and rinse gently with water.
Cover the stain with crystal violet and let sit for the alotted time. Pour off the
crystal violet and rinse gently with water. - ANSWER✔✔ 1: Pass one side of a
clean slide through a micro burner to remove dust.
,2: Spread your bacterial sample on the slide, using an inoculating loop, in an area
about the size of a quarter. Allow the smear to dry.
3: Heat-fix the slide by passing it quickly through the flame of a micro burner 2 or
3 times.
4: Cover the stain with crystal violet and let sit for the alotted time. Pour off the
crystal violet and rinse gently with water.
5: Cover the slide with iodine and let sit for the alotted time. Pour off the iodine
and rinse gently with water.
6: Hold the slide at a 45o angle over the sink and allow drops of ethanol to flow
over the smear. Rinse gently with water.
7: Cover the smear with safranin and let sit for the alotted time. Pour off the
safranin and rinse gently with water.
For each of the following common Genera of bacteria, tell if they are Gram
positive or Gram negative:
Enterobacter
Streptococcus
Staphylococcus
Proteus - ANSWER✔✔ Gram -: Enterobacter
, Gram +: Streptococcus
Gram +: Staphylococcus
Gram -: Proteus
In a properly conducted Gram stain, what color will Gram negative cells be
immediately after staining with crystal violet? - ANSWER✔✔ purple
Which solution is used to de-coloize the cells in the Gram staining process? -
ANSWER✔✔ 95% ethanol
In a properly conducted Gram stain, what color will gram-negative cells be after
fixing with iodine? - ANSWER✔✔ purple
What is the purpose of each of the reagents used in the Gram stain?
95% Ethyl Alcohol
Crystal Violet
Gram's Iodine
Safranin - ANSWER✔✔ Decolorizer: 95% Ethyl Alcohol
Primary stain: Crystal Violet
Mordant: Gram's Iodine
Secondary stain: Safranin
For each of the following statements about the Gram stain answer TRUE or FALSE.
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