BIOL 3201 Exam 1 Study Guide
Questions with Solved Solutions
2026/2027 Edition.
brightfield microscope - Answer - simplest form of microscopy where light is either passed
through, or reflected off, a specimen. Illumination is not altered by devices that change the
properties of light (such as polarizers or filters). Requires the use of stains to visualize cells.
phase contrast microscope - Answer - converts the differences in optical density (refractive
index) of cells into different shades of brightness (contrast). Allows for the visualization of
morphology, external structures, and some internal structures. Stains are not required.
darkfield microscope - Answer - contrast is created by a bright specimen on a dark
background. It is ideal for revealing morphology and external structures, but does not provide a
great deal of information about internal structure. Stains are not required.
fluorescent microscope - Answer - uses high intensity illumination to excite fluorescent
molecules (fluorophores) in the sample. When a molecule absorbs photons, electrons are
excited to a higher energy level. As electrons 'relax' back to the ground-state, vibrational energy
is lost and, as a result, the emission spectrum is shifted to longer wavelengths. Fluorescence
emanates from the sample (and not the illuminating light). Requires use of fluorophores.
immersion oil - Answer oil with the same refractive index as glass. used with the 100x
objective. immersion oil fills the gap between the objective and slide to form a continuous lens
path which increases image resolution by reducing light refraction
parfocal - Answer the ability of a microscope to remain relatively in focus when changing from
lower power objective to a higher power objective
numerical aperture - Answer a mathematical expression that describes how the condenser
lens concentrates and focuses the light rays from the light source
resolving power - Answer the ability of a lens system to show two closely spaced objects as
distinct and separate
working distance - Answer the distance between the bottom of the objective lens and the
slide
80% - Answer bacteria are transparent when viewed without stain by brightfield microscopy
because they are composed of approximately __ water
, simple stain - Answer staining with a ... allows microbiologists to visualize cell morphology, cell
arrangement, and internal storage materials
differential - Answer the Gram stain is a ... stain
crystal violet, Gram's iodine, ethanol, safranin - Answer correct order of Gram staining
procedure
catalase - Answer aerobic bacteria produce the enzyme ..., which is tested by dropping
hydrogen peroxide ob a sample.
positive; negative - Answer Staphylococcus is aerobic and tests ... for the catalase test while
the aerotolerant Streptococcus and Enterococcus are ...
oxidase test - Answer consists of swabbing a sample with a cotton swab, adding reagent, then
seeing if it turns blue or not. must be interpreted within 30 seconds because oxygen can create
a false positive
KOH test - Answer verification supplement to Gram staining; consists of adding KOH to a
sample and seeing if it becomes stringy
positive - Answer Gram negative = KOH ... and vice versa
selective medium - Answer a media that will allow only certain microorganisms to grow and
will inhibit the growth og other microorganisms
MSA - Answer an example of selective medium is the incorporation of sodium chloride into ...
that selects for the genus Staphylococcus (and other sodium tolerant organisms) but inhibits the
growth of bacteria that cannot tolerate the salt concentration
differential medium - Answer a media that can differentiate microorganisms based on a
change in their appearance
Staphylococcus aureus - Answer when ... grows on msa, it ferments mannitol producing acid
and changing a pH indicator in the media from red to yellow around the colonies. some other
species of Staphylococcus cannot ferment mannitol
SBA - Answer ... is a type of differential medium that show different levels of blood cell lysis.
Questions with Solved Solutions
2026/2027 Edition.
brightfield microscope - Answer - simplest form of microscopy where light is either passed
through, or reflected off, a specimen. Illumination is not altered by devices that change the
properties of light (such as polarizers or filters). Requires the use of stains to visualize cells.
phase contrast microscope - Answer - converts the differences in optical density (refractive
index) of cells into different shades of brightness (contrast). Allows for the visualization of
morphology, external structures, and some internal structures. Stains are not required.
darkfield microscope - Answer - contrast is created by a bright specimen on a dark
background. It is ideal for revealing morphology and external structures, but does not provide a
great deal of information about internal structure. Stains are not required.
fluorescent microscope - Answer - uses high intensity illumination to excite fluorescent
molecules (fluorophores) in the sample. When a molecule absorbs photons, electrons are
excited to a higher energy level. As electrons 'relax' back to the ground-state, vibrational energy
is lost and, as a result, the emission spectrum is shifted to longer wavelengths. Fluorescence
emanates from the sample (and not the illuminating light). Requires use of fluorophores.
immersion oil - Answer oil with the same refractive index as glass. used with the 100x
objective. immersion oil fills the gap between the objective and slide to form a continuous lens
path which increases image resolution by reducing light refraction
parfocal - Answer the ability of a microscope to remain relatively in focus when changing from
lower power objective to a higher power objective
numerical aperture - Answer a mathematical expression that describes how the condenser
lens concentrates and focuses the light rays from the light source
resolving power - Answer the ability of a lens system to show two closely spaced objects as
distinct and separate
working distance - Answer the distance between the bottom of the objective lens and the
slide
80% - Answer bacteria are transparent when viewed without stain by brightfield microscopy
because they are composed of approximately __ water
, simple stain - Answer staining with a ... allows microbiologists to visualize cell morphology, cell
arrangement, and internal storage materials
differential - Answer the Gram stain is a ... stain
crystal violet, Gram's iodine, ethanol, safranin - Answer correct order of Gram staining
procedure
catalase - Answer aerobic bacteria produce the enzyme ..., which is tested by dropping
hydrogen peroxide ob a sample.
positive; negative - Answer Staphylococcus is aerobic and tests ... for the catalase test while
the aerotolerant Streptococcus and Enterococcus are ...
oxidase test - Answer consists of swabbing a sample with a cotton swab, adding reagent, then
seeing if it turns blue or not. must be interpreted within 30 seconds because oxygen can create
a false positive
KOH test - Answer verification supplement to Gram staining; consists of adding KOH to a
sample and seeing if it becomes stringy
positive - Answer Gram negative = KOH ... and vice versa
selective medium - Answer a media that will allow only certain microorganisms to grow and
will inhibit the growth og other microorganisms
MSA - Answer an example of selective medium is the incorporation of sodium chloride into ...
that selects for the genus Staphylococcus (and other sodium tolerant organisms) but inhibits the
growth of bacteria that cannot tolerate the salt concentration
differential medium - Answer a media that can differentiate microorganisms based on a
change in their appearance
Staphylococcus aureus - Answer when ... grows on msa, it ferments mannitol producing acid
and changing a pH indicator in the media from red to yellow around the colonies. some other
species of Staphylococcus cannot ferment mannitol
SBA - Answer ... is a type of differential medium that show different levels of blood cell lysis.
