Biology 1406 Lab Exam 1 questions
and answers
To reduce the amount of light rays that are refracted away from the objective lens. It increases
numerical aperture and maintains a uniform light speed. increase the resolving power of a
microscope. Prevents refraction of light. - correct answer ✔✔ Why is oil immersion used?
Illuminator-The light source for the microscope. Diaphragm-Controls the amount of light
entering the condenser. Condenser lens- Focuses light through the specimen. - correct answer
✔✔ What parts of the microscope does light travel through?
multiply magnification of eyepiece by magnification of the objective. - correct answer ✔✔ How
do you calculate total magnification?
Ocular Micrometer's Pitch Length (under the microscope) =
[Actual Micrometer Pitch Length］ ÷ ［Objective Lens Magnification］
7 stage units = 10 ocular units
Then: 7 stage units is equivalent to .07 mm (7 x .01 = .07 mm)
𝐶 = .07 10
𝐶 = .007 𝑚𝑚
Convert to μm: .oo7 mm = 7 μm
For this specific objective: one increment on ocular scale is equivalent to 7 μm - correct answer
✔✔ calibrating microscope ocular micrometer(calculation)
To enhance visualization of the cell or certain cellular components under a microscope - correct
answer ✔✔ Why do we use stains on microscope slides?
, Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan (50-90% of cell
envelope), and as a result are stained purple by crystal violet, whereas gram-negative bacteria
have a thinner layer (10% of cell envelope), so do not retain the purple stain and are counter-
stained pink by the Safranin. - correct answer ✔✔ What does gram staining do?
Simple stains(1 stain is used) differential stain(2 or more stains) - correct answer ✔✔ How is
gram staining different?
+ appear blue or purple, stains the bacteria itself. - appear pink or red, stains the background of
bacteria. Can help determine shape. - correct answer ✔✔ What is the difference between gram
negative and gram positive (+,-)?
- correct answer ✔✔ given a diagram with ocular micrometer and looking through
microscope....know how to know how many units this would be?(formula)
- correct answer ✔✔ know examples of kinds of things that we might measure in micrometers
vs nanometer vs millimeters (what would be the right unit to measure something like this?)
-Write out your procedure or reference a protocol Materials Required (Pre-lab: Complete prior
to coming to lab.)
• Describe required materials.
• Include proper safety precautions
Procedure (Pre-lab/During Lab: Complete prior to coming to lab; modify as needed during lab)
• Pre-lab: Describe the step by step guidelines for all experimental procedures you intend to
perform in lab. Include a citation to identify your sources.
• During lab: Fill in any gaps or add/adjust the protocol as necessary.
• Hint: Be sufficiently detailed that anyone could read your methods and duplicate your
experiment. Write it as if you were giving direction for someone else to do the lab. - correct
answer ✔✔ What goes in materials and methods section of your notebook?
and answers
To reduce the amount of light rays that are refracted away from the objective lens. It increases
numerical aperture and maintains a uniform light speed. increase the resolving power of a
microscope. Prevents refraction of light. - correct answer ✔✔ Why is oil immersion used?
Illuminator-The light source for the microscope. Diaphragm-Controls the amount of light
entering the condenser. Condenser lens- Focuses light through the specimen. - correct answer
✔✔ What parts of the microscope does light travel through?
multiply magnification of eyepiece by magnification of the objective. - correct answer ✔✔ How
do you calculate total magnification?
Ocular Micrometer's Pitch Length (under the microscope) =
[Actual Micrometer Pitch Length］ ÷ ［Objective Lens Magnification］
7 stage units = 10 ocular units
Then: 7 stage units is equivalent to .07 mm (7 x .01 = .07 mm)
𝐶 = .07 10
𝐶 = .007 𝑚𝑚
Convert to μm: .oo7 mm = 7 μm
For this specific objective: one increment on ocular scale is equivalent to 7 μm - correct answer
✔✔ calibrating microscope ocular micrometer(calculation)
To enhance visualization of the cell or certain cellular components under a microscope - correct
answer ✔✔ Why do we use stains on microscope slides?
, Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan (50-90% of cell
envelope), and as a result are stained purple by crystal violet, whereas gram-negative bacteria
have a thinner layer (10% of cell envelope), so do not retain the purple stain and are counter-
stained pink by the Safranin. - correct answer ✔✔ What does gram staining do?
Simple stains(1 stain is used) differential stain(2 or more stains) - correct answer ✔✔ How is
gram staining different?
+ appear blue or purple, stains the bacteria itself. - appear pink or red, stains the background of
bacteria. Can help determine shape. - correct answer ✔✔ What is the difference between gram
negative and gram positive (+,-)?
- correct answer ✔✔ given a diagram with ocular micrometer and looking through
microscope....know how to know how many units this would be?(formula)
- correct answer ✔✔ know examples of kinds of things that we might measure in micrometers
vs nanometer vs millimeters (what would be the right unit to measure something like this?)
-Write out your procedure or reference a protocol Materials Required (Pre-lab: Complete prior
to coming to lab.)
• Describe required materials.
• Include proper safety precautions
Procedure (Pre-lab/During Lab: Complete prior to coming to lab; modify as needed during lab)
• Pre-lab: Describe the step by step guidelines for all experimental procedures you intend to
perform in lab. Include a citation to identify your sources.
• During lab: Fill in any gaps or add/adjust the protocol as necessary.
• Hint: Be sufficiently detailed that anyone could read your methods and duplicate your
experiment. Write it as if you were giving direction for someone else to do the lab. - correct
answer ✔✔ What goes in materials and methods section of your notebook?
