Module 3 Flashcards
A nanometer is defined as:
10 -9 or one-billionth of a meter
True or False: A nanometer is longer than a micrometer
F
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 can still be seen as separate. Poor or low resolution means two or more objects may appear as one.
Contrast on the other hand is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of
a sunny afternoon (bright light against 2 dark objects = high contrast).
Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the magnification of a sample.
A. Objective
B. Condenser
C. Iris diaphragm
D. Eye piece
A.
Only the oculars (eyepiece) and the objectives contribute to the magnification of the sample. Since the eyepiece is fixed, only the objectives could be altered.Objective
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 Diaphram
What is the total magnification on (relative to your eye) of a sample imaged with a 60x objective and a 10x eyepiece? Show your math.
60x objective x 10x ocular = 600x magnification
True or False: Staining is often required to image a cell that is adherent and flat (thin).
True
True or False: A cell that is adherent, flat (thin), and unstained is easily identified using bright field microscopy
False
Which of the following could be seen clearly by the unaided eye? Select all that apply.
A. Bacteria with diameter of 24 μm
B. Protozoa with diameter of 150 μm
C. Virus with a diameter of 0.2 μm
D. Skin cell with diameter of 1500 μm
B. Protozoa with diameter of 150 μm
D. Skin cell with diameter of 1500 μm
The unaided eye can, on average, clearly resolve objects > 100 μm
Which of the following could NOT be seen clearly by the unaided eye? Select all that apply.
A. Bacteria with diameter of 24 μm
B. Protozoa with diameter of 150 μm
C. Virus with a diameter of 0.2 μm
D. Skin cell with diameter of 1500 μm
A. Bacteria with diameter of 24 μm
C. Virus with a diameter of 0.2 μm
The unaided eye can, on average, clearly resolve objects > 100 μm
Label the following unmarked microscope components (numbered arrows) by matching it with the components provided
(letters).
1F- eyepiece
2D- neck
3B- fine adjustment knob
4G- objective
5A- stage
6H- base
This type of microscope is best suited for visualizing GFP, RFP, and YFP proteins.
Fluorescence
This type of microscope utilizes ultraviolet (UV) light to illuminate stained objects.
Florescence
This type of microscope uses a specialized condenser and objective to amplify the slight differences between cells and background.
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 uses neither halogen nor UV light sources but rather lasers to illuminate stained cells in high resolution.
Confocal
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.
(picture labeled B)
The image was captured using a Scanning Electron Microscope (SEM). The above image shows the trademark ‘shell’ image (no subcellular organelles are visible) reminiscent of SEM. Only TEM is capable of visualizing subcellular substrucutres.
Identify what type of electron microscope was used to capture the following image and explain your choice.
(picture labeled A)
The above image is captured via a Transmission Electron Microscope (TEM). Even at 20nm resolution (inset image), subcellular substructures are still visible. The image lacks the outside ‘shell’ only appearance of SEM.
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: A Giemsa stain can be used to determine the presence of pathogenic bacteria.
True
True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane.
True
True or False: Following the decolorization step of the Gram stain, Gram-Negative bacteria will appear colorless.
True
True or False: If you wish to study the motiity of an organism you cannot heat fix, but you can chemically fix the specimen
False
Name one substance capable of chemically fixing cells to a slide.
Any of the following are true: Paraformaldehyde, ethanol or methanol.
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 with TB, describe what you would expect to see on the stained slide.
I would expect to see red cells (TB+) on a blue background (TB negative).
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 stainining and crystal violet could be used.
True or False: If a patient is suspected of having malaria, a Giemsa stain would be an appropriate differential test to perform.
True
Giesma stains are often used in the clinical setting aid in the diagnosis of blood parasites.
A human blood sample from a patient with a suspected parasite needs to be stained for diagnosis. Which stain should be selected?
Giemsa
Select the type of microscopy used to generate the image:
(black background with green glowing cells)
Florescence microscopy
You are the lead technician in the Microbiology Department’s core Microscopy lab. You are given a list what different scientists would like to observe in their samples. You must match these samples with appropriate type of microscopy.
- A slide stained with fuchsin simple stain to observe the size of the cells
- The organelles in a living ciliate
- An unstained sample that cannot be visualized with bright field because microorganism absorbs very little light
- Theprotein trafficking of tagged proteins of interest under experimental conditions in a cell
- Build a 3-dimensional image of a cell
A. Bright field
B. Phase contrast
C. Dark field
D. Florescence
E. Confocal
- A
- B
- C
- D
- E
What is the total magnification (relative to your eye) of a sample imaged with a 20x objective and a 15x eyepiece? Show your math.
20 x 15 = 300x magnification
A researcher is asked to determine which of two vials contains E coli and which contains Salmonella. Knowing both are Gram-Negative while only one of them is capable of fermenting lactose, which type of media would be best suited:
A. Growth media
B. Differential media
C. Selective media
D. Selective and Differential media
B
True or False: LB agar is classified as a selective, non-differential media.
False
True or False: A Giemsa stain can be used to determine the presence of pathogenic bacteria.
True
. True or False: Following the decolorization step of the Gram stain, Gram-Negative bacteria will appear colorless.
True
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
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 would be the easiset technique and I would use crystal violet during this process.
Name one substance capable of chemically fixing cells to a slide
methanol, ethanol, or paraformaldehyde
True or False: Following the decolorization step of the Gram Stain, Gram-Negative bacteria will appear colorless
True
