Portage Microbiology
micrometer - ANS one millionth of a meter, 10^ -6
nanometer - ANS one billionth of a meter, 10^-9
Resolution - ANS the distance between two objects at which the objects still can be seen as
separate
What happens if the resolution is poor? - ANS Poor or low resolution means two (or more)
objects may appear as one.
Contrast - ANS the difference in light absorbance between two objects.
What happens if there is poor contrast? - ANS gives a high background and makes the
visualization of multiple objects difficult.
If you wish to increase the amount of light going into a microscope, what part would you adjust?
- ANS The iris diaphragm
As light passes through a microscope, what is the last piece that light passes before reaching
your eyes? - ANS the ocular lens, or eyepiece, directly into your eye.
How is the total magnification of an object calculated? - ANS Total magnification is calculated
by multiplying the power of the objective and the power of the eyepiece.
What is one limitation of fixing your sample? - ANS Fixation requires you to irreversibly kill your
sample. Thus, determining the motility (cell movement) of a sample is impossible. Fixation also
runs the risk of distorting the specimen shape and arrangement.
Phase-contrast microscopy provided what benefits to imaging? - ANS Phase-contrast
microscope can provide detailed images of live cells without staining. Able to visualize certain
structures that would otherwise be invisible
What is the distinguishing feature of dark field microscopy? - ANS dark field microscopy reflects
light off of the specimen at an angle. The resulting image is an exceptionally dark background
and a vibrant specimen.
Unlike brightfield microscope, fluorescence microscopes illuminate samples through what
spectrum? - ANS Fluorescence microscopes illuminate samples through the UV Spectrum.
What is the primary difference between TEM and SEM? - ANS During transmission electron
microscopy the electron passes through the sample whereas during scanning electron
microscopy the electron is reflected off the sample creating a three dimensional 'shell' model of
the specimen.
Gram staining is based on what basic principle? - ANS Gram staining, developed by Hans
Christian Gram in 1884, began with the basic observation that different types of bacteria react
differently to various dyes. Some bacteria readily take up a specific dye while others do not.
What is a key determinant in a bacteria being Gram-positive? - ANS Gram-positive bacteria
have a thick peptidoglycan layer. The Gram stain exploits this characteristic by using the dye
combinations of Crystal violet and Iodine. Crystal violet is retained by the thick peptidoglycan
cell wall and forms a stable complex with iodine (upon its addition) effectively trapping the dyes
in the cell. The resulting mixture is a purple coloration of the cell.
What is the purpose of heat fixing a sample? - ANS Heat fixing ensures the samples tightly
adhere to the glass slide prior to staining (and washing) procedures.
What is the primary purpose of a wet mount? - ANS Wet mounts are most often performed to
visualize live cells as well as the motility and behavior of an organism.
micrometer - ANS one millionth of a meter, 10^ -6
nanometer - ANS one billionth of a meter, 10^-9
Resolution - ANS the distance between two objects at which the objects still can be seen as
separate
What happens if the resolution is poor? - ANS Poor or low resolution means two (or more)
objects may appear as one.
Contrast - ANS the difference in light absorbance between two objects.
What happens if there is poor contrast? - ANS gives a high background and makes the
visualization of multiple objects difficult.
If you wish to increase the amount of light going into a microscope, what part would you adjust?
- ANS The iris diaphragm
As light passes through a microscope, what is the last piece that light passes before reaching
your eyes? - ANS the ocular lens, or eyepiece, directly into your eye.
How is the total magnification of an object calculated? - ANS Total magnification is calculated
by multiplying the power of the objective and the power of the eyepiece.
What is one limitation of fixing your sample? - ANS Fixation requires you to irreversibly kill your
sample. Thus, determining the motility (cell movement) of a sample is impossible. Fixation also
runs the risk of distorting the specimen shape and arrangement.
Phase-contrast microscopy provided what benefits to imaging? - ANS Phase-contrast
microscope can provide detailed images of live cells without staining. Able to visualize certain
structures that would otherwise be invisible
What is the distinguishing feature of dark field microscopy? - ANS dark field microscopy reflects
light off of the specimen at an angle. The resulting image is an exceptionally dark background
and a vibrant specimen.
Unlike brightfield microscope, fluorescence microscopes illuminate samples through what
spectrum? - ANS Fluorescence microscopes illuminate samples through the UV Spectrum.
What is the primary difference between TEM and SEM? - ANS During transmission electron
microscopy the electron passes through the sample whereas during scanning electron
microscopy the electron is reflected off the sample creating a three dimensional 'shell' model of
the specimen.
Gram staining is based on what basic principle? - ANS Gram staining, developed by Hans
Christian Gram in 1884, began with the basic observation that different types of bacteria react
differently to various dyes. Some bacteria readily take up a specific dye while others do not.
What is a key determinant in a bacteria being Gram-positive? - ANS Gram-positive bacteria
have a thick peptidoglycan layer. The Gram stain exploits this characteristic by using the dye
combinations of Crystal violet and Iodine. Crystal violet is retained by the thick peptidoglycan
cell wall and forms a stable complex with iodine (upon its addition) effectively trapping the dyes
in the cell. The resulting mixture is a purple coloration of the cell.
What is the purpose of heat fixing a sample? - ANS Heat fixing ensures the samples tightly
adhere to the glass slide prior to staining (and washing) procedures.
What is the primary purpose of a wet mount? - ANS Wet mounts are most often performed to
visualize live cells as well as the motility and behavior of an organism.
