Biol 240L Lab Final Exam Questions With
Correct Answers
What |are |simple |stains |used |for? |- |CORRECT |ANSWER✔✔-Determining |the |size, |shape |and |
arrangement |of |bacterial |cells
How |do |positive |staining |procedures |work? |- |CORRECT |ANSWER✔✔-The |stain |has |a |positively |
charged |chromophore, |so |the |negatively |charged |bacterial |outer |surface |will |be |attracted |to |
the |chromophores |to |stain |the |organism
Why |are |slides |heat |fixed |prior |to |staining? |- |CORRECT |ANSWER✔✔-1.) |Kill |Bacteria
2.) |Adherence |to |slide
3.) |Sample |will |more |readily |take |up |stains
What |are |some |simple |dyes |used |for |simple |staining |procedures? |- |CORRECT |ANSWER✔✔--
methylene |blue
- |basic |fuchsin
- |crystal |violet
What |are |the |shapes |of |E. |coli |and |Bs. |Bacilli? |- |CORRECT |ANSWER✔✔-coccus |and |rod |shapes,
|respectively
How |do |you |calculate |the |magnification |of |specimens |under |a |microscope? |- |CORRECT |
ANSWER✔✔-size |of |specimen |(in |μm) |/ |actual |size |of |image |(in |μm)
What |type |of |staining |technique |is |the |gram |stain? |- |CORRECT |ANSWER✔✔-differential |stain
, Gram-positive |bacteria |- |CORRECT |ANSWER✔✔-- |bacteria |that |do |not |have |an |outer |
membrane
- |will |stain |purple |during |the |gram |stain |procedure
What |are |Gram-negative |bacteria, |and |how |do |they |appear |during |the |Gram-stain |procedure?
|- |CORRECT |ANSWER✔✔-- |bacteria |that |have |an |outer |membrane
- |will |stain |red |during |the |gram |stain |procedure
mordant; |what |is |an |example |of |a |mordant |in |the |gram |stain |procedure? |- |CORRECT |
ANSWER✔✔-A |substance |added |to |a |staining |solution |to |make |it |stain |more |intensely; |iodine
decolorizing |agent |- |CORRECT |ANSWER✔✔-a |solution |used |in |the |process |of |removing |a |stain
Why |do |gram |positive |bacteria |stain |purple? |- |CORRECT |ANSWER✔✔-they |are |stained |by |the |
crystal |violet |stain, |and |will |hold |the |stain |in |their |membrane |so |it |cannot |be |removed |by |a |
decolorizing |agent |and |will |then |not |be |stained |by |the |counter |staining |dye.
Why |do |gram |negative |bacteria |stain |red? |- |CORRECT |ANSWER✔✔-they |do |not |readily |hold |
the |crystal |violet |dye |in |their |membrane, |so |the |dye |will |be |removed |by |the |decolorizing |
agent |and |they |will |be |stained |by |the |counter |stain.
What |factors |affect |a |bacterium's |reaction |to |the |Gram |stain? |- |CORRECT |ANSWER✔✔-- |
culture |age
- |pH |of |the |medium
Under |what |conditions |may |a |gram-positive |bacterial |culture |stain |as |if |they |are |gram-
negative, |and |why? |- |CORRECT |ANSWER✔✔-Older |cultures |and |those |grown |in |acidic |
mediums |stain |as |gram-negative |cultures |because |their |cell |walls |have |been |degraded.
Correct Answers
What |are |simple |stains |used |for? |- |CORRECT |ANSWER✔✔-Determining |the |size, |shape |and |
arrangement |of |bacterial |cells
How |do |positive |staining |procedures |work? |- |CORRECT |ANSWER✔✔-The |stain |has |a |positively |
charged |chromophore, |so |the |negatively |charged |bacterial |outer |surface |will |be |attracted |to |
the |chromophores |to |stain |the |organism
Why |are |slides |heat |fixed |prior |to |staining? |- |CORRECT |ANSWER✔✔-1.) |Kill |Bacteria
2.) |Adherence |to |slide
3.) |Sample |will |more |readily |take |up |stains
What |are |some |simple |dyes |used |for |simple |staining |procedures? |- |CORRECT |ANSWER✔✔--
methylene |blue
- |basic |fuchsin
- |crystal |violet
What |are |the |shapes |of |E. |coli |and |Bs. |Bacilli? |- |CORRECT |ANSWER✔✔-coccus |and |rod |shapes,
|respectively
How |do |you |calculate |the |magnification |of |specimens |under |a |microscope? |- |CORRECT |
ANSWER✔✔-size |of |specimen |(in |μm) |/ |actual |size |of |image |(in |μm)
What |type |of |staining |technique |is |the |gram |stain? |- |CORRECT |ANSWER✔✔-differential |stain
, Gram-positive |bacteria |- |CORRECT |ANSWER✔✔-- |bacteria |that |do |not |have |an |outer |
membrane
- |will |stain |purple |during |the |gram |stain |procedure
What |are |Gram-negative |bacteria, |and |how |do |they |appear |during |the |Gram-stain |procedure?
|- |CORRECT |ANSWER✔✔-- |bacteria |that |have |an |outer |membrane
- |will |stain |red |during |the |gram |stain |procedure
mordant; |what |is |an |example |of |a |mordant |in |the |gram |stain |procedure? |- |CORRECT |
ANSWER✔✔-A |substance |added |to |a |staining |solution |to |make |it |stain |more |intensely; |iodine
decolorizing |agent |- |CORRECT |ANSWER✔✔-a |solution |used |in |the |process |of |removing |a |stain
Why |do |gram |positive |bacteria |stain |purple? |- |CORRECT |ANSWER✔✔-they |are |stained |by |the |
crystal |violet |stain, |and |will |hold |the |stain |in |their |membrane |so |it |cannot |be |removed |by |a |
decolorizing |agent |and |will |then |not |be |stained |by |the |counter |staining |dye.
Why |do |gram |negative |bacteria |stain |red? |- |CORRECT |ANSWER✔✔-they |do |not |readily |hold |
the |crystal |violet |dye |in |their |membrane, |so |the |dye |will |be |removed |by |the |decolorizing |
agent |and |they |will |be |stained |by |the |counter |stain.
What |factors |affect |a |bacterium's |reaction |to |the |Gram |stain? |- |CORRECT |ANSWER✔✔-- |
culture |age
- |pH |of |the |medium
Under |what |conditions |may |a |gram-positive |bacterial |culture |stain |as |if |they |are |gram-
negative, |and |why? |- |CORRECT |ANSWER✔✔-Older |cultures |and |those |grown |in |acidic |
mediums |stain |as |gram-negative |cultures |because |their |cell |walls |have |been |degraded.
