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BIOD 171 Portage Learning Exam 3 Latest Update
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BIOD 171 Portage Learning Exam 3 Latest UpdateDefine the following measures: micrometer and nanometer. - ANSWER A micrometer is
one-millionth of a meter and a nanometer is one-billionth of a meter.
What are the two key factors that determine whether or not you can see an object? -
ANSWER The resolution and the contrast. Resolution is the distance between two
objects where you can still see them as separate. Contrast is the difference in light
between two objects.
If you wanted to let more light into a microscope, which part would you change? -
ANSWER The iris diaphragm.
As light travels through a microscope, what is the last piece of that light goes through
before it reaches your eyes? - ANSWER After light passes through the sample and the
objective lens it passes through the OCULAR LENS.
How would you work out the total magnification of an object? - ANSWER You times it
with the power of the objective and the power of the eyepiece.
What is one limitation of fixing your sample? - ANSWER Fixing your sample requires you
to irreversibly kill your sample.
This can eliminate the ability to tell the movement of the cell. You could distort the shape
and structure.
What benefits does phase-contrast microscopy confer to imaging? - ANSWER Phase
contrast microscopy provides detailed pictures without staining.
What is the characteristic that is unique to dark field microscopy? - ANSWER Dark field
microscopy reflects light off of the specimen at an angle.
, Unlike the brightfieqld microscope, fluorescence microscopes illuminate samples
through what spectrum? - ANSWER The Ultraviolet Spectrum.
What is the fundamental difference between TEM and SEM? - ANS The electron passes
through the sample during TEM where as the electron is reflected off the sample during
SEM.
Gram staining is based on what basic principle? - ANS With the basic observation that
different types of bacteria react differently to various dyes.
What is one of major determining factors in whether or not a bacteria is Gram-positive?
-ANSWER Gram-positives have a thick peptidoglycan layer. Uses crystal violet and
iodine. Resulting mixture purple coloration of the cell.
What is the purpose of a heat fix of a sample? -ANSWER Heat fixing makes sure the
samples are tightly adhere to the glass slide.
What is the main reason that a wet mount would be done? ANSWER Wet mounts are
often done to be able to view living cells and in order to observe an organism's motility
and behaviour.
The acid-fast stain is used most frequently for the identification of which specific
microorganism? ANSWER Mycobacterium tuberculosis is the most common for an
acid-fast stain.
What is the total magnification of a specimen that is being imaged with a 60x objective
and a 10x eyepiece? - ANSWER 60 x 100 = 600x magnification
True or False: An attached, flat, unstained cell can be easily observed with bright field
microscopy. - ANSWER False
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