Test 3 Flashcards
. A nanometer is defined as…
10^-9 or one billionth
Resolution and contrast are two critical factors that influence your ability to see an object. Explain each
Resolution refers to the 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.
Contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult.
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
Iris diaphragm
A micrometer is defined as…
one-millionth of a meter and is commonly designated at 10-6
What is the total magnification (relative to your eye) of a sample imaged with a 60x objective and a 10x eyepiece? Show your math
Total Magnification = Objective x Eyepiece = 60 x 10 = 600x larger
True or False: A cell that is adherent, flat (thin), and unstained is easily identified using bright field microscopy. Why?
False, Adherent, flat cells are almost invisible due to the limits on both resolution and contrast
Which of the following could NOT be seen clearly by the unaided eye?Select all that apply.
Virus with a diameter of 0.2 μm
Bacteria with diameter of 24 μm
The unaided eye can, on average, clearly resolve objects> 100 μm
This type of microscope is best suited for visualizing GFP, RFP, and YFP proteins
Fluorescence
This type of microscope can provide detailed images of live cells without staining
Phase-Contrast
This type of microscope enhances contrast between specimen and background but does not permit the visualization of intracellular structures.
dark field
This type of microscope is capable of capturing images in multiple focal planes, rendering a specimen in 3-D
confocal
Identify what type of electron microscope was used to capture the following image and explain your choice
A scanning electron microscope (SEM) was used because this is a 3D detailed shell model. Also, the subcellular structures of the organelles are not visible, a TEM microscope would be needed to do so.
Gram-Positive cells appear [answer1] in color due to a [answer2]peptidoglycan layer in the cell wall.
Purple
Thick
Gram-Negative cells appear [answer1] in color due to a [answer2]peptidoglycan layer in the cell wall
Pink
Thin
True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane.
True
True or False: If you wish to study the motility of an organism you cannot heat fix, but you can chemically fix the specimen. Why?
False, both heat and chemicals kill the cell
You want to observe the size and shape of a cell. What is the easiest staining technique that you could perform? Name at least one dye you would use during this process
Simple stain. You could use any of the following: methylene blue, crystal violet, safranin or fuschin.
You suspect a patient may have TB. Once a sample has been obtained, it is sent off to the lab for an acid-fast stain. If the patient were infected withTB, describe what you would expect to see on the stained slide
If the patient were infected with TB there would be red cells on blue background. The red cells indicate that the patient is infected with TB
True or False: If a patient is suspected of having malaria, a Giemsa stain would be an appropriate differential test to perform. Why?
True, Giemsa stains are often used in the clinical setting to aid in the diagnosis of blood parasites
Identify what type of electron microscope was used to capture the following image and explain your choice.
Transmission Electron microscope (TEM) was use to capture the following image because there is visualization of subcellular organelles in the specimen even at 20nm resolution. Also it has no 3D detailed shell model
A gram stain has been attempted on an unknown sample, and it was found to have a high degree of resistance to decolorization. Given this property, which stain should be attempted next?
Acid-fast staining
Identify what type of microscope was used to capture the following image and explain your choice
Brightfield Microscope, cells are unstained and appear almost invisible
Identify the type of microscope used. Explain
Phase contrast microscopes, still lacks stain, but image contains much more detail and certain structures appear visible.
Identify the type of microscope used. Explain
Darkfield microscopy, the background is dark, while the sample appears illuminated. Often used for spirochete borrelia specimens - cause of lyme disease
