Biol 211 Exam 1 Potential Questions With Perfect
Solutions
A student completes a Gram stain on a bacterial smear that has a mix of gram-
negative and gram-positive organisms. The student stops the procedure
without adding safranin. What would be the outcome of the Gram stain?
Correct Answer - The gram-positive organisms would appear purple, and
the gram-negative organisms would be colorless
In the Gram stain, what is the purpose of the counterstain? Correct Answer
- To make gram-negative cells visible
In the Gram stain, crystal violet remains in gram-positive cells after treatment
with alcohol because crystal violet-iodine complexes are trapped _______.
Correct Answer - In thick layers of peptidoglycan
Your lab partner tells you the bacteria are moving in his Gram-stained smear.
You can conclude that __________. Correct Answer - He didn't properly fix
the smear
Before cells are stained, the specimen must be fixed. Fixing a specimen
accomplishes all of the following EXCEPT which one? Correct Answer -
Fixation differentiates the various cells being observed
In the Gram strain, if the decolorizing step is deleted, gram-negative cells will
appear ____ at the completion of the staining procedure. Correct Answer -
Purple
In the Gram stain, what is the purpose of the decolorizer? Correct Answer -
To selectively remove stain from cells
____ is an example of an acidic dye; ____ is an example of a basic dye. Correct
Answer - Nigrosine; Crystal violet
Which of the following staining procedures is correctly matched with the
principle use for that particular strain? Correct Answer - Endospore
stain to distinguish dormant structures formed during adverse environmental
conditions
, In the Gram-stain procedure, a clear oval in the center of a cell could indicate
___ Correct Answer - The presence of an endospore
____ is important in medical terminology because the results help physicians
select appropriate antibiotics for treatment Correct Answer - Gram
staining
Acid-fast Mycobacteria differ from non-acid-fast bacteria by the presence of
__________. Correct Answer - Wavy material in their cell walls
What is the correct order for the Gram stain process? Correct Answer -
Crystal violet -> iodine -> decolorizer -> safranin
In the Gram stain, crystal violet is the ____ Correct Answer - Primary
stain
Consider a gram-positive cell in a hypertonic medium. If the peptidoglycan
were damaged, the cell would __________. Correct Answer - Shrink
Many pathogenic (disease-producing) bacteria produce a(n) __________ that
protects them from phagocytosis by host cells. Correct Answer - Capsule
Which of the following is NOT a structure of prokaryotic cells? Correct
Answer - Chloroplasts
Chemotaxis refers to the ability of microorganisms to ____ Correct Answer -
Move towards or away from chemical stimuli
Why is penicillin selectively toxic to bacterial cells but harmless to human
cells? Correct Answer - Penicillin specifically weakens peptidoglycan,
which is found only in bacterial cells
You are observing a Gram stain of rod-shaped microorganisms that are linked
in a chain and stained purple. How would you describe these bacteria using
the correct terminology of the cell shaped and arrangement? Correct
Answer - Gram-positive streptobacilli
Solutions
A student completes a Gram stain on a bacterial smear that has a mix of gram-
negative and gram-positive organisms. The student stops the procedure
without adding safranin. What would be the outcome of the Gram stain?
Correct Answer - The gram-positive organisms would appear purple, and
the gram-negative organisms would be colorless
In the Gram stain, what is the purpose of the counterstain? Correct Answer
- To make gram-negative cells visible
In the Gram stain, crystal violet remains in gram-positive cells after treatment
with alcohol because crystal violet-iodine complexes are trapped _______.
Correct Answer - In thick layers of peptidoglycan
Your lab partner tells you the bacteria are moving in his Gram-stained smear.
You can conclude that __________. Correct Answer - He didn't properly fix
the smear
Before cells are stained, the specimen must be fixed. Fixing a specimen
accomplishes all of the following EXCEPT which one? Correct Answer -
Fixation differentiates the various cells being observed
In the Gram strain, if the decolorizing step is deleted, gram-negative cells will
appear ____ at the completion of the staining procedure. Correct Answer -
Purple
In the Gram stain, what is the purpose of the decolorizer? Correct Answer -
To selectively remove stain from cells
____ is an example of an acidic dye; ____ is an example of a basic dye. Correct
Answer - Nigrosine; Crystal violet
Which of the following staining procedures is correctly matched with the
principle use for that particular strain? Correct Answer - Endospore
stain to distinguish dormant structures formed during adverse environmental
conditions
, In the Gram-stain procedure, a clear oval in the center of a cell could indicate
___ Correct Answer - The presence of an endospore
____ is important in medical terminology because the results help physicians
select appropriate antibiotics for treatment Correct Answer - Gram
staining
Acid-fast Mycobacteria differ from non-acid-fast bacteria by the presence of
__________. Correct Answer - Wavy material in their cell walls
What is the correct order for the Gram stain process? Correct Answer -
Crystal violet -> iodine -> decolorizer -> safranin
In the Gram stain, crystal violet is the ____ Correct Answer - Primary
stain
Consider a gram-positive cell in a hypertonic medium. If the peptidoglycan
were damaged, the cell would __________. Correct Answer - Shrink
Many pathogenic (disease-producing) bacteria produce a(n) __________ that
protects them from phagocytosis by host cells. Correct Answer - Capsule
Which of the following is NOT a structure of prokaryotic cells? Correct
Answer - Chloroplasts
Chemotaxis refers to the ability of microorganisms to ____ Correct Answer -
Move towards or away from chemical stimuli
Why is penicillin selectively toxic to bacterial cells but harmless to human
cells? Correct Answer - Penicillin specifically weakens peptidoglycan,
which is found only in bacterial cells
You are observing a Gram stain of rod-shaped microorganisms that are linked
in a chain and stained purple. How would you describe these bacteria using
the correct terminology of the cell shaped and arrangement? Correct
Answer - Gram-positive streptobacilli
