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Biology 156 Lab Practical 3 Exam Questions and Answers
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Biology 156 Lab Practical 3 Exam Questions and Answers
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Biology 156: Lab Practical 3 ExamQuestions and Answers
2 domains that contain prokaryotes - Answer -Bacteria and Archaea
2 benefits of bacteria - Answer -1. some bacteria are decomposers, which break down
organic material (e.g. sewage treatment), 2. many bacteria in the human body help
facilitate functions which aid in digestion
Human diseases caused by bacteria - Answer -pneumonia, tuberculosis, gonorrhea,
syphilis, chlamydia, cholera, tetnus, botulism, bubonic plague, lyme disease
What is the purpose of fixing the smear? - Answer -The purpose of fixing a smear is to
make cells stick to the slide, kill bacteria in the smear, and allow for optimal capability
for retaining any stains performed
2 methods of fixing the smear - Answer -heat fixation and chemical fixation
Heat fixation - Answer -kills the cells, destroying autolytic enzymes, and causes the
cells to adhere to the slide
chemical fixation - Answer -In microscopy, a technique that uses methyl alcohol or
formalin to attach a smear to a slide.
advantage of viewing an unstained specimen - Answer -advantage of viewing an
unstained specimen is that it doesn't require heat fixation, allowing it to be viewed in its
original unaltered form. This is important because some cells are too delicate to
undergo the heat from heat-fixation. by only staining the background and leaving the
bacteria unstained (i.e. negative staining), the cell's shape and size is preserved and
observed
3 stains used in simple staining procedures - Answer -methylene blue, gram safranin,
gram crystal violet
when are negative stains used - Answer -on cells that are too difficult (e.g. spirilla) or
too delicate to undergo the heat from heat-fixation. by only staining background and
leaving the bacteria unstained, the cell's true morphological shape, size,and
arrangement can be accurately observed and recorded, without altering (shrinking or
swelling the cell)
, how many stains are used in differential staining procedures - Answer -2 stains are
used in differential stains (as opposed to just one stain). each stain has a different name
first tain is primary stain, second is called countertain. common example of differential
staining is the gram stain. acid fast stain is also an example of differential staining.
Why is alcohol important during the gram-staining technique? - Answer -without alcohol,
the gram-negative bacterium will remain purple because the outer lipopolysaccharide
layer will retain its structural integrity (i.e. not be broken down by the acid from the
alcohol)
gram positive - Answer -stains purple
gram negative - Answer -pink
Kinyoun method - Answer -phenol concentrations and carbol fuchsin concentration are
increased to such a point that heating is not necessary.
Why should Gram stain not be used to stain acid-fast organisms? - Answer -acid-fast
organisms such as myobacteria have lipid in their cell walls (i.e. myolic acid) making it
hard to leave a stain
acid fast stain - Answer -carbolfuchsin used to stain Mycobacterium species
Acid fast organisms - Answer -Mycobacterium and Nocardia (e.g. myobacterium
tuberculosis, myobacterium leprae)
Tuberculosis - Answer -caused by the acid-fast organism known as Mycobacterium
tuberculosis
Leprosy (Hansen's Disease) - Answer -caused by mycobacterium leprae
Diplo
Strepto
Staphylo
Tetrad
Sarcina - Answer -name 5 common arrangements of cocci
diplo - Answer -pairs
strepto - Answer -chains
staphylo - Answer -grape-like clusters
tetrads - Answer -groups of four
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