PORTAGE MICROBIOLOGY EXAM #3 WITH QUESTIONS AND
ANSWERS
A micrometer is defined as - -10^-6
-A nanometer is defined as - -10^-9
-Assuming a constant (non-adjustable) light source power, identify the part of the microscope you would
adjust to limit the amount of light entering the microscope (multiple choice) - -The iris diaphragm
-Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the
magnification of a sample - -Objective
-Contrast (short answer) - -Difference in light absorbance between two objects. Poor contrast gives a
high background and makes the visualization of multiple objects difficult.
-Gram-Negative cells appear _____ in color due to a _____ peptidoglycan layer in the cell wall (fill in the
blanks) - -Pink, thin
-Gram-Positive cells appear _____ in color due to a _____ peptidoglycan layer in the cell wall (fill in the
blanks) - -Purple, thick
-Identify what type of electron microscope was used to capture the following image and explain your
choice - -A: TEM, shows 2-D rendering
B: SEM shows 3-D shell models
-Label the following unmarked microscope components by matching it with the components provided - -
1. Eyepiece
2. Neck
3. Fine adjustment knob
4. Objective
5. Stage
6. Base
-Name one substance capable of chemically fixing cells to a slide - -Paraformaldehyde, ethanol, or
methanol
-Resolution (short answer) - -Distance between two objects at which the objects still can be seen as
separate. Poor or low resolution means two (or more) objects may appear as one
-This type of microscope can provide detailed images of live cells without staining (given list of
microscopes) - -Phase-Contrast
-This type of microscope is best suited for visualizing GFP, RFP and YFP proteins (given list of
microscopes) - -Flourescence
ANSWERS
A micrometer is defined as - -10^-6
-A nanometer is defined as - -10^-9
-Assuming a constant (non-adjustable) light source power, identify the part of the microscope you would
adjust to limit the amount of light entering the microscope (multiple choice) - -The iris diaphragm
-Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the
magnification of a sample - -Objective
-Contrast (short answer) - -Difference in light absorbance between two objects. Poor contrast gives a
high background and makes the visualization of multiple objects difficult.
-Gram-Negative cells appear _____ in color due to a _____ peptidoglycan layer in the cell wall (fill in the
blanks) - -Pink, thin
-Gram-Positive cells appear _____ in color due to a _____ peptidoglycan layer in the cell wall (fill in the
blanks) - -Purple, thick
-Identify what type of electron microscope was used to capture the following image and explain your
choice - -A: TEM, shows 2-D rendering
B: SEM shows 3-D shell models
-Label the following unmarked microscope components by matching it with the components provided - -
1. Eyepiece
2. Neck
3. Fine adjustment knob
4. Objective
5. Stage
6. Base
-Name one substance capable of chemically fixing cells to a slide - -Paraformaldehyde, ethanol, or
methanol
-Resolution (short answer) - -Distance between two objects at which the objects still can be seen as
separate. Poor or low resolution means two (or more) objects may appear as one
-This type of microscope can provide detailed images of live cells without staining (given list of
microscopes) - -Phase-Contrast
-This type of microscope is best suited for visualizing GFP, RFP and YFP proteins (given list of
microscopes) - -Flourescence
