Biology 156: Lab Practical 3
2 domains that contain prokaryotes correct answersBacteria and Archaea
2 benefits of bacteria correct answers1. 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 correct answerspneumonia, tuberculosis, gonorrhea, syphilis,
chlamydia, cholera, tetnus, botulism, bubonic plague, lyme disease
What is the purpose of fixing the smear? correct answersThe 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 correct answersheat fixation and chemical fixation
Heat fixation correct answerskills the cells, destroying autolytic enzymes, and causes the cells to adhere
to the slide
chemical fixation correct answersIn microscopy, a technique that uses methyl alcohol or formalin to
attach a smear to a slide.
advantage of viewing an unstained specimen correct answersadvantage 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 correct answersmethylene blue, gram safranin, gram crystal
violet
, when are negative stains used correct answerson 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 correct answers2 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? correct answerswithout 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 correct answersstains purple
gram negative correct answerspink
Kinyoun method correct answersphenol 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? correct answersacid-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 correct answerscarbolfuchsin used to stain Mycobacterium species
Acid fast organisms correct answersMycobacterium and Nocardia (e.g. myobacterium tuberculosis,
myobacterium leprae)
Tuberculosis correct answerscaused by the acid-fast organism known as Mycobacterium tuberculosis
Leprosy (Hansen's Disease) correct answerscaused by mycobacterium leprae
2 domains that contain prokaryotes correct answersBacteria and Archaea
2 benefits of bacteria correct answers1. 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 correct answerspneumonia, tuberculosis, gonorrhea, syphilis,
chlamydia, cholera, tetnus, botulism, bubonic plague, lyme disease
What is the purpose of fixing the smear? correct answersThe 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 correct answersheat fixation and chemical fixation
Heat fixation correct answerskills the cells, destroying autolytic enzymes, and causes the cells to adhere
to the slide
chemical fixation correct answersIn microscopy, a technique that uses methyl alcohol or formalin to
attach a smear to a slide.
advantage of viewing an unstained specimen correct answersadvantage 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 correct answersmethylene blue, gram safranin, gram crystal
violet
, when are negative stains used correct answerson 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 correct answers2 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? correct answerswithout 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 correct answersstains purple
gram negative correct answerspink
Kinyoun method correct answersphenol 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? correct answersacid-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 correct answerscarbolfuchsin used to stain Mycobacterium species
Acid fast organisms correct answersMycobacterium and Nocardia (e.g. myobacterium tuberculosis,
myobacterium leprae)
Tuberculosis correct answerscaused by the acid-fast organism known as Mycobacterium tuberculosis
Leprosy (Hansen's Disease) correct answerscaused by mycobacterium leprae
