Microbiology Lab Exam 1- Biol 2120 Questions And 100% Accurate Answers.
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Microbiology Lab
What was the purpose of this microscope laboratory experiment? - Answer to name the parts of a compound light microscope and their functions, learn the correct way to use the c.l.m
what is the difference between magnification and resolution? - Answer magnification: uses special lenses to e...
Microbiology Lab Exam 1- Biol 2120
Questions And 100% Accurate Answers.
What was the purpose of this microscope laboratory experiment? - Answer to name the parts of a
compound light microscope and their functions, learn the correct way to use the c.l.m
what is the difference between magnification and resolution? - Answer magnification: uses special
lenses to enlarge image of an object.
resolution: separates or distinguishes structures to close together
what is the purpose of placing immersion oil on the slide? - Answer prevents scattering of light
what are the advantages of electron microscope as compared to light microscopes? - Answer electron
microscopes: uses electron beam
light microscope: uses lights to visualize object
two major differences between prokaryotic cells & eukaryotic cells - Answer prokaryotic cells: single
celled & no nucleus
eukaryotic cells: membrane bound nucleus & DNA
if the ocular magnification is 40x and the oil immersion objective is in place, what is the total
magnification? - Answer 40X x 100= 4000X
what is simple staining? - Answer when one stain is used to examine shape and arrangement of
bacteria
what is the purpose of the smear prep lab experiment? - Answer 1. to prepare a bacterial smear
2. study bacterial morphology
,why should one make sure that the commercially available glass slide does not have a layer of grease
before preparing the smear? - Answer 1. To get an even stain
2. Because the stain and smear will not stay
what would happen if you had skipped the heat fixing step and continued with the staining procedure? -
Answer the bacterial cells on the slide would shift when the agents are being rinsed off which would
mean the bacteria would go down the drain.
what is the reason for sterilizing the whole wire and part of the handle of the inoculating loop before
and after each transfer? - Answer to ensure that the bacteria is free of contamination from other
microorganisms.
list the most common shapes and arrangements of bacteria and provide a specific example of each: -
Answer cocci: oval/round: streptococcus pneumonae
bacilli: rod shaped: bacillus anthrasis
spirillum: spiral with one or more twists
why is knowing the bacterial shapes and arrangement important? - Answer enables scientists to
determine what type of bacteria it is and what methods need to be used to control growth
what is the purpose of negative staining - Answer to identification of certain bacteria or structures that
are normally difficult to stain
why is the technique called "negative staining" - Answer the bacteria is not stained but the the
background is. the bacteria appears clear while the background looks dark
why does nigrosin not stain bacterial cells/structures? - Answer nigrosin is negatively charged and are
repelled by bacteria that have the same negative charge.
give 2 situations where the negative staining procedure would be used. - Answer 1. used to accentuate
capsules that surround certain bacteria/yeasts
2. used to determine if known bacterial infections are either gram+ or gram- bacteria due to the
composition of the cell wall.
, what is the purpose of the streak plate method? - Answer isolate pure colonies of bacteria
on which of the sections of the plate do u see isolated colonies. explain this distribution. - Answer
section 3. as we streak through sections 1 & 2 we decrease the streak to 3 which causes isolated
colonies.
give 2 reasons why you might have a situation in which bacterial colonies were found on the first section
of a steak plate, but not on sections two and three. - Answer 1. you missed the bacteria in section
when you tried to streak it through section 2 & 3.
2. the bacteria dried up before you could streak it to the next sections.
how would you determine which colonies might be contaminants on a streak plate? - Answer different
color/appearance
what was the purpose of gram staining the bacteria? - Answer to determine if a bacteria is either
gram+ or gram-
what would happen if you do not apply gram's iodine after staining with crystal violet? - Answer the
violet will not be pushed into the cell wall and the gram+ cells would get decolorized by the alcohol &
appear to be gram-
explain the mechanism of gram staining - Answer stain cells with crystal violet, rinse then add iodine
which traps the stain inside the cell. when the alcohol is applied the gram- bacteria lose the outer
membrane which allows the crystal violet staining inside to be washed away & allow for these to be
counterstained with safranin, leaving them red.
differences between cell wall of gram- and gram+ bacteria - Answer gram negative: thin & red
gram positive: thick & purple
what is the purpose of the acid-fast staining technique? - Answer to identify the bacteria belonging to
genus mycobacterium
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