MCB 101 MIDTERM PREP QUESTIONS WITH VERIFIED
ANSWERS
Aseptic Technique - Answers - Techniques carried out under sterile conditions, free of
microorganisms
Disinfection - Answers - __________ dramatically reduces the number of bacteria
present, but does not necessarily sterilize a surface
Sterilization - Answers - Renders a surface or substance free of microorganisms
Autoclaving - Answers - ____________ is the predominant method of sterilization used
to sterilize lab equipment and media
- Heats the material, using pressurized steam, to 121 degrees Celsius and a pressure of
15 psi for 20-30 minutes
Vortex mixer - Answers - A __________ can be used to achieve a homogeneous
mixture of cells
Streak Plate - Answers - The _________ __________ is the most common method for
isolating a microorganism in pure culture
Mixed - Answers - If a streak is done from a _________ culture, there will be multiple
colony types or morphologies present on the plate
Spread plates - Answers - ___________ ___________ are used for measuring the
number of viable cells in a sample
Streak, spread - Answers - In ___________ plates, the cells are diluted as they are
plated. In _________ plates, the cells are diluted before they are plated
30-300 - Answers - What is the ideal range for the number of colonies that should be
present on a spread plate?
Serial Dilution - Answers - A culture that is diluted sequentially
Resolution - Answers - The sharpness of an image formed by an optical system
Resolving Power - Answers - A measure of the ability of an optical system to form
separate and distinct images of two objects
RP= (Wavelength)/ (2 x Numerical Aperture) - Answers - What is the resolving power
equation?
,100X - Answers - For which objective do you have to put immersion oil on the slide?
40X - Answers - For which objective should you never use immersion oil?
0.2= 660 nm/ 2 (NA)
NA= 1.65 - Answers - If the wavelength of light is 660 nm and the resolving power is 0.2
micrometers, what is the numerical aperture?
Cocci - Answers - Spherically shaped bacteria
Staphylococci - Answers - Irregular clusters of spherically shaped bacteria
Streptococci - Answers - One-dimensional chains of spherically shaped bacteria
Sarcinae - Answers - Cube-shaped packets of spherically shaped bacteria
Bacilli - Answers - Rod-shaped bacterial cells
Heat fixing - Answers - When the back of a bacterial slide is passed through the flame
of a Bunsen burner three times after it has air dried, melting the complex carbohydrates
of the bacterial cell walls to the glass, causing the cell to stick to the slide
Slight haze - Answers - A properly prepared smear should appear as a ________
________ when the slide is held up to a light
Original Concentration= Number of colonies x dilution factor/ volume plated (in mL) -
Answers - What is the equation to determine the cells in an original culture?
Dilution Factor - Answers - The inverse of the dilution
Original Concentration= (40) (10^6)/ (0.1 mL)
= 4x10^8 - Answers - If a dilution is 10^-6, the number of colonies observed is 40, and
the volume plated is 100 microliters, what is the original concentration of cells?
A - Answers - What should you do when you first pick up your inoculating loop?
A. Flame sterilize it from stem to loop
B. Sterilize it by dipping it ethanol then passing it through the flame of your Bunsen
burner
C. Make sure the wire is straight
D. Flame sterilize just the loop
E. Sterilize it by dipping it into ethanol
F - Answers - When you are finished using your microscope, what should you do?
A. Lower the stage
B. Rotate the nosepiece to move the 100X objective away from the stage
, C. Dispose of your slide in the sharps container
D. Wipe oil from the 100X objective with lens paper
E. Turn off the light source
F. All of the above
Streak - Answers - The goal of a __________ plate is to generate pure culture
media
Spread - Answers - A ____________ plate dilutes cells prior to inoculating
Spread - Answers - The goal of a __________ plate is to determine original
CFU/mLStreak
Streak - Answers - A __________ plate dilutes cells by mechanical separation on the
media
D - Answers - Increasing which of the following will improve the resolution of the image
seen in the microscope?
A. Wavelength of the light used to illuminate the specimen
B. Intensity of the light used to illuminate the specimen
C. Magnification of the objective used to view the specimen
D. Numerical aperature of the lens used to view the specimen
Original Concentration= (236) (10^7)/ (0.1)
= 2.36x10^10 - Answers - A student plates 100 µL of a 10-7 dilution of E. coli culture on
a Luria Agar plate. After 24 hours, 236 colonies have grown on the plate. What was the
original concentration of the culture in CFU/mL?
E - Answers - Why is it important to allow a sterilized inoculating loop to cool before
attempting to sample liquid culture?
A. To prevent contamination
B. To prevent damaging agar plates
C. To avoid killing all of the bacteria
D. To avoid damaging the culture tube
E. To avoid creating aerosals
Stain - Answers - A dye consisting of a chromophore and a counter ion to balance
charge
Positively, negatively - Answers - __________ charged stains directly bind to bacteria
while __________ charged stains are repelled from bacteria
Simple - Answers - ___________ stains stain all cells in the same way
Differential - Answers - ___________ stains stain cells differently based on some
physical characteristic
ANSWERS
Aseptic Technique - Answers - Techniques carried out under sterile conditions, free of
microorganisms
Disinfection - Answers - __________ dramatically reduces the number of bacteria
present, but does not necessarily sterilize a surface
Sterilization - Answers - Renders a surface or substance free of microorganisms
Autoclaving - Answers - ____________ is the predominant method of sterilization used
to sterilize lab equipment and media
- Heats the material, using pressurized steam, to 121 degrees Celsius and a pressure of
15 psi for 20-30 minutes
Vortex mixer - Answers - A __________ can be used to achieve a homogeneous
mixture of cells
Streak Plate - Answers - The _________ __________ is the most common method for
isolating a microorganism in pure culture
Mixed - Answers - If a streak is done from a _________ culture, there will be multiple
colony types or morphologies present on the plate
Spread plates - Answers - ___________ ___________ are used for measuring the
number of viable cells in a sample
Streak, spread - Answers - In ___________ plates, the cells are diluted as they are
plated. In _________ plates, the cells are diluted before they are plated
30-300 - Answers - What is the ideal range for the number of colonies that should be
present on a spread plate?
Serial Dilution - Answers - A culture that is diluted sequentially
Resolution - Answers - The sharpness of an image formed by an optical system
Resolving Power - Answers - A measure of the ability of an optical system to form
separate and distinct images of two objects
RP= (Wavelength)/ (2 x Numerical Aperture) - Answers - What is the resolving power
equation?
,100X - Answers - For which objective do you have to put immersion oil on the slide?
40X - Answers - For which objective should you never use immersion oil?
0.2= 660 nm/ 2 (NA)
NA= 1.65 - Answers - If the wavelength of light is 660 nm and the resolving power is 0.2
micrometers, what is the numerical aperture?
Cocci - Answers - Spherically shaped bacteria
Staphylococci - Answers - Irregular clusters of spherically shaped bacteria
Streptococci - Answers - One-dimensional chains of spherically shaped bacteria
Sarcinae - Answers - Cube-shaped packets of spherically shaped bacteria
Bacilli - Answers - Rod-shaped bacterial cells
Heat fixing - Answers - When the back of a bacterial slide is passed through the flame
of a Bunsen burner three times after it has air dried, melting the complex carbohydrates
of the bacterial cell walls to the glass, causing the cell to stick to the slide
Slight haze - Answers - A properly prepared smear should appear as a ________
________ when the slide is held up to a light
Original Concentration= Number of colonies x dilution factor/ volume plated (in mL) -
Answers - What is the equation to determine the cells in an original culture?
Dilution Factor - Answers - The inverse of the dilution
Original Concentration= (40) (10^6)/ (0.1 mL)
= 4x10^8 - Answers - If a dilution is 10^-6, the number of colonies observed is 40, and
the volume plated is 100 microliters, what is the original concentration of cells?
A - Answers - What should you do when you first pick up your inoculating loop?
A. Flame sterilize it from stem to loop
B. Sterilize it by dipping it ethanol then passing it through the flame of your Bunsen
burner
C. Make sure the wire is straight
D. Flame sterilize just the loop
E. Sterilize it by dipping it into ethanol
F - Answers - When you are finished using your microscope, what should you do?
A. Lower the stage
B. Rotate the nosepiece to move the 100X objective away from the stage
, C. Dispose of your slide in the sharps container
D. Wipe oil from the 100X objective with lens paper
E. Turn off the light source
F. All of the above
Streak - Answers - The goal of a __________ plate is to generate pure culture
media
Spread - Answers - A ____________ plate dilutes cells prior to inoculating
Spread - Answers - The goal of a __________ plate is to determine original
CFU/mLStreak
Streak - Answers - A __________ plate dilutes cells by mechanical separation on the
media
D - Answers - Increasing which of the following will improve the resolution of the image
seen in the microscope?
A. Wavelength of the light used to illuminate the specimen
B. Intensity of the light used to illuminate the specimen
C. Magnification of the objective used to view the specimen
D. Numerical aperature of the lens used to view the specimen
Original Concentration= (236) (10^7)/ (0.1)
= 2.36x10^10 - Answers - A student plates 100 µL of a 10-7 dilution of E. coli culture on
a Luria Agar plate. After 24 hours, 236 colonies have grown on the plate. What was the
original concentration of the culture in CFU/mL?
E - Answers - Why is it important to allow a sterilized inoculating loop to cool before
attempting to sample liquid culture?
A. To prevent contamination
B. To prevent damaging agar plates
C. To avoid killing all of the bacteria
D. To avoid damaging the culture tube
E. To avoid creating aerosals
Stain - Answers - A dye consisting of a chromophore and a counter ion to balance
charge
Positively, negatively - Answers - __________ charged stains directly bind to bacteria
while __________ charged stains are repelled from bacteria
Simple - Answers - ___________ stains stain all cells in the same way
Differential - Answers - ___________ stains stain cells differently based on some
physical characteristic
