MCB2010L Midterm Exam Questions With
Accurate Answers
The path of light through the lenses of the scope results in - ANSWER E. A & B
Image enlargement; Inversion of the image
Total Magnification= - ANSWER C. Objective X Ocular
The numerical aperture is an optical value stamped on the lens by the
microscope manufacturer and is a function of the light gathering capacity of the
lens - ANSWER True
The greater the numerical aperture, the better the resolution of the microscope
using that lens - ANSWER True
The refractive index of the oil is the same as the glass of slide and lens, so no
light is refracted before entering the lens - ANSWER True
Staining is used to increase the contrast between bacteria and the slide in order
to clearly visualize the cells. This can be accomplished by using a negatively
charged stain that interacts with the cell surface to make the cells darker than
the background - ANSWER False
Types of bacterial cell morphology include: - ANSWER E. All of the above
Types of bacterial cell morphology include: - ANSWER E. All of the above
How many rod shaped bacterial cells are found in Vibrio, Spirilla, or Spirochete -
ANSWER A. None
What is the correct procedure for negative stain? - ANSWER B. Add Congo Red
stain, mix bacterial in stain, spread stain and bacteria across slide, air dry.
A negative stain is based on the principle that a dye that has a negative charge
is repelled by the negative charge of the bacterial cell - ANSWER True
The lipids of Mycobacterium repel the negative stain because of the chemical
nature of their cell walls - ANSWER True
After negative staining the bacterial cell should remain colorless - ANSWER
True
, Negative staining can be accomplished using crystal violet, methylene blue,
nigrosin, or Congo Red - ANSWER False
As you increase the magnification of your objective, the field of view on your
sample decreases - ANSWER True
Slime layers are more readily sloughed off than capsules - ANSWER True
Describe the appearance of colonies encapsulated bacteria - ANSWER E. All of
the above- Smooth; Shiny; Gooey; Slimy
With negative staining, bacterial capsules appear as a clear halo surrounding
the cell - ANSWER True
When encapsulated bacterial cells are stained with Congo red and the
background is stained with acid fuchsin, you will see pink cells surrounded by a
halo with a blue background - ANSWER True
When unencapulated bacterial cells are stained with Congo Red and the
background is stained with acid fuchsin, you will see pink organisms in a blue
background - ANSWER True
A virulence factor is anything associated with a pathogen that decreases its
ability to cause harm to its host - ANSWER False
The capsule may inhibit phagocytosis by white blood cells, reduce bacterial
dehydration, provide antigenic variability, serve as means for nutrient
accumulation or can be used for attachment - ANSWER True
S. mutans causes dental caries and uses a flagella to attach to teeth - ANSWER
False
Bacterial numbers can be estimated by turbidity and spectrophotometry -
ANSWER True
When a cell suspension is placed in the light path of a spectrophotometer the
photocell measures the light absorbed by the suspension - ANSWER True
Microorganisms in the environment usually exist as a mixed population -
ANSWER True
To identify and study the organisms, one must use a pure culture - ANSWER
True
Accurate Answers
The path of light through the lenses of the scope results in - ANSWER E. A & B
Image enlargement; Inversion of the image
Total Magnification= - ANSWER C. Objective X Ocular
The numerical aperture is an optical value stamped on the lens by the
microscope manufacturer and is a function of the light gathering capacity of the
lens - ANSWER True
The greater the numerical aperture, the better the resolution of the microscope
using that lens - ANSWER True
The refractive index of the oil is the same as the glass of slide and lens, so no
light is refracted before entering the lens - ANSWER True
Staining is used to increase the contrast between bacteria and the slide in order
to clearly visualize the cells. This can be accomplished by using a negatively
charged stain that interacts with the cell surface to make the cells darker than
the background - ANSWER False
Types of bacterial cell morphology include: - ANSWER E. All of the above
Types of bacterial cell morphology include: - ANSWER E. All of the above
How many rod shaped bacterial cells are found in Vibrio, Spirilla, or Spirochete -
ANSWER A. None
What is the correct procedure for negative stain? - ANSWER B. Add Congo Red
stain, mix bacterial in stain, spread stain and bacteria across slide, air dry.
A negative stain is based on the principle that a dye that has a negative charge
is repelled by the negative charge of the bacterial cell - ANSWER True
The lipids of Mycobacterium repel the negative stain because of the chemical
nature of their cell walls - ANSWER True
After negative staining the bacterial cell should remain colorless - ANSWER
True
, Negative staining can be accomplished using crystal violet, methylene blue,
nigrosin, or Congo Red - ANSWER False
As you increase the magnification of your objective, the field of view on your
sample decreases - ANSWER True
Slime layers are more readily sloughed off than capsules - ANSWER True
Describe the appearance of colonies encapsulated bacteria - ANSWER E. All of
the above- Smooth; Shiny; Gooey; Slimy
With negative staining, bacterial capsules appear as a clear halo surrounding
the cell - ANSWER True
When encapsulated bacterial cells are stained with Congo red and the
background is stained with acid fuchsin, you will see pink cells surrounded by a
halo with a blue background - ANSWER True
When unencapulated bacterial cells are stained with Congo Red and the
background is stained with acid fuchsin, you will see pink organisms in a blue
background - ANSWER True
A virulence factor is anything associated with a pathogen that decreases its
ability to cause harm to its host - ANSWER False
The capsule may inhibit phagocytosis by white blood cells, reduce bacterial
dehydration, provide antigenic variability, serve as means for nutrient
accumulation or can be used for attachment - ANSWER True
S. mutans causes dental caries and uses a flagella to attach to teeth - ANSWER
False
Bacterial numbers can be estimated by turbidity and spectrophotometry -
ANSWER True
When a cell suspension is placed in the light path of a spectrophotometer the
photocell measures the light absorbed by the suspension - ANSWER True
Microorganisms in the environment usually exist as a mixed population -
ANSWER True
To identify and study the organisms, one must use a pure culture - ANSWER
True
