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MED 103- BIOLOGY I > 13. SCIENTIFIC STUDY OF CELLS (MICROSCOPY) > Flashcards

13. SCIENTIFIC STUDY OF CELLS (MICROSCOPY) Flashcards

1
Q
  1. What are all organisms made of?
A
  • cells
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2
Q
  1. Provide a definition for a cell?
A
  • it is the basic structural and functional unit of every organism
  • it is the simplest collection of living matter
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3
Q
  1. What is cell structure related to?
A
  • it is related to the cellular function
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4
Q
  1. What relates all cells?
A
  • their descent from earlier cells
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5
Q
  1. What are two techniques used for the scientific study of cells?
A
  1. Microscopy
  2. Cell Fractionation
    (the isolation of sub-cellular structures)
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6
Q
  1. What can we not see with the naked eye?
A
  • cells
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7
Q
  1. How do biologists study cells?
A
  • with the help of microscopes and biochemical tools
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8
Q
  1. What are the two types of cell microscopes used to study cell structures?
A
  • Light Microscopes (LMs)
  • Electron Microscopes (EMs)
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9
Q
  1. What are two characteristics of Light Microscopes?
A
  • visible light passes through a specimen
  • cellular structures are magnified using lenses
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10
Q
  1. What is one characteristic of Electron Microscopes?
A
  • they focus a beam of electrons through a specimen
    (TEM)
  • and onto its surface
    (SEM)
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11
Q
  1. What does TEM stand for?
A
  • Transmission electron microscopes
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12
Q
  1. What does SEM stand for?
A
  • Scanning electron microscope
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13
Q
  1. When was the electron microscope invented?
    What did it show?
A
  • in the 1930s
  • it showed the smaller internal structure of organelles
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14
Q
  1. What are three factors that affect the image quality produced by a microscope?
A
  1. Magnification
  2. Resolution
  3. Contrast
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15
Q
  1. What is the Magnification of a Microscope?
A
  • it is the ratio of an object’s image size
    TO its real size
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16
Q
  1. What is the Resolution of a Microscope?
A
  • it is the measure of the clarity of the image
  • it is the minimum distance of two distinguishable points
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17
Q
  1. What is the Contrast of a Microscope?
A
  • it is the visible differences in parts of the sample
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18
Q
  1. What do different Light Microscopes do?
A
  • they use different methods for enhancing the visualisation of cellular structures
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19
Q
  1. What are the Six types of methods used by the Microscope to enhance the visualisation of cellular structures?
A
  1. Brightfield
    (unstained specimen)
  2. Brightfield/Compound
    (stained specimen)
  3. Phase- Contrast
  4. Differential-Interference Contrast
    (Nomarski)
  5. Fluorescence
  6. Confocal
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20
Q
  1. What is the Brightfield Unstained Specimen Technique?
A
  • passes light directly through the specimen
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21
Q
  1. What is the result of using the Brighfield Unstained Specimen technique?
A
  • the image has little contrast
    (unless the cell is naturally pigmented or artificially stained)
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22
Q
  1. What is the Brightfield Stained Specimen Technique?
A
  • it is staining the specimen with various dyes
  • this enhances the contrast
  • most staining procedures require that the cells be fixed
    (preserved)
    (this means that they can be dead cells)
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23
Q
  1. What are the results of using the Brightfield Stained Specimen technique?

What dye is usually used to stain the cheek epithelial cell?

A
  • methenyl blue
24
Q
  1. What technique is used to make holes in the cells for the dyes to enter?

What does this do to the cell?

A
  • Nebulisation
  • this kills the cell
25
Q
  1. What is the Phase-Contrast technique?
A
  • it enhances the contrast in unstained cells
  • it does this by amplifying variations in the density without the specimen
    (the area surrounding the specimen)
26
Q
  1. What are the results of the Phase-Contrast technique?

When is this technique very useful?

A
  • it is useful for examining living un-pigmented cells
    (such as dividing cells)
27
Q
  1. Which two techniques are used by the same microscope?
    What is the only difference between them?
A
  • the Brightfield Unstained Specimen and the Brightfield
    stained specimen
  • the only difference is that one involves a artificially
    pigmented cell and the other does not
28
Q
  1. What is the Differential - Interference- Contrast
    technique?
    (Nomarski)
A
  • it is very similar to Phase-Contrast Microscopy
  • it is more advanced and more 3D than the Phase-Contrast Microscope
  • it uses optical modifications to exaggerate the differences in the density
  • this almost makes the image look 3D
29
Q
  1. What is the Fluorescence Technique?
A
  • it shows the locations of specific molecules in the cell
  • it does this by tagging the molecules with fluorescent dyes or fluorescent antibodies
  • these fluorescent substances absorb Ultraviolet (UV) radiation
  • they use this to emit visible light
30
Q
  1. What is the Confocal technique?
A
  • it uses lasers and special optics
  • it uses these to “optically section” fluorescently stained
    specimens
  • only a single plane of focus is illuminated
  • the computer subtracts any out-of-focus fluorescence
    above and below the plane that is being focused on
  • it is the only technique that produces 3D images
31
Q
  1. What is the result of using the Confocal Technique?
A
  • a sharp image
  • the nerve cells are green
  • the support cells are red
  • the regions of overlap are yellow
32
Q
  1. What does the blurry bottom Fluorescence photograph allow for?
A
  • it allows for the reconstruction of three-dimensional structures from the obtained images
33
Q
  1. By how many times can Light Microscopes magnify the samples they are analysing?
A
  • by 1000 times of the actual specimen
34
Q
  1. What is the resolution of the Light Microscope (LM)?
A
  • 0.2 um (micrometer)
  • this is equal to 200 nm (nanometers)
35
Q
  1. What kind of structures are too small to be resolved by Light Microscopes?
A
  • most sub-cellular structures
  • these include:
    • organelles
    • membrane enclosed compartments
36
Q
  1. What does the Electron Microscope use to magnify its subjects?
A
  • it uses a beam of electrons
  • these are concentrated by applying a strong magnetic
    field
37
Q
  1. What is the maximum magnification achieved by an Electron Microscope?
A
  • it can magnify up to 250 000 x (times)
38
Q
  1. What is the smallest structure an Electron Microscope can detect?
    Give an example of a structure this small.
A
  • a structure as small as 0.1nm (nanometer)

EG: virus

39
Q
  1. What can the Electron Microscope detect?
    Give three examples.
A
  • macromolecules
  • These include:
    - proteins
    - DNA
    - polysaccharides
40
Q
  1. What are the two types of electron microscopes used to study sub cellular structures?
A
  1. Transmission Electron Microscopes (TEM)
  2. Scanning Electron Microscopes (SEM)
41
Q
  1. What are two characteristics of Transmission Electron Microscopes?
A
  • they focus a beam of electrons through a specimen
  • they are mainly used to study the internal structure of cells
    (2D images)
42
Q
  1. What are three characteristics of Scanning Electron Microscopes?
A
  • they focus a beam of electrons onto the surface of a specimen
  • they provide 3D images
  • they are used to study the surface (external structure) of the specimen
43
Q
  1. What does the Transmission Electron Microscope provide images of?
    Give an example of this.
A
  • it provides images of the internal ultrastructure of cells
  • it provides 2D images

EG: images of a thin specimen section
: cilia were cut out along their lengths
: this created a longitudinal section
: the cilia cut straight across produced cross sections

44
Q
  1. What images does the Scanning Electron Microscope (SEM) produce?
    Give an example of this.
A
  • it produces images of the surface of a specimen
  • they are 3D images

EG: the surface of the cell from a rabbit windpipe
: it is covered with cilia (motile organelles)
: beating the cilia helps to move the inhaled debris
upward towards the throat

45
Q
  1. What are Cristae?
A
  • they are found in the mitochondria
  • they are folds
  • they increase the surface area
  • this produces ATP faster
46
Q
  1. What is Cell Fractionation?

FRACTIONATE= divide into fractions or components

A
  • it is a process that enables the isolation of sub-cellular components
  • this determines the functions of the organelle
  • it fractionates cells
  • this separates the major organelles from one another
47
Q
  1. What does Cell Fractionation base its separation of organelles on?
A
  • density
  • size
48
Q
  1. What is Centrifugation?
    Provide an example.
A
  • the centrifuge is used to fractionate cells
  • it fractionates them into their component parts
  • EG: ultracentrifuges
    : they isolate even the smallest components at very
    fast speeds
49
Q
  1. What are the two types of Centrifugation?
A
  1. Differential Centrifugation
  2. Density Gradient Centrifugation
50
Q
  1. What is Differential Centrifugation?
A
  • it is the separation of the cell based on the size only
  • the smallest component that you can isolate is placed largely in the centrifuge
  • a sucrose concentration constant is used
51
Q
  1. What is Density Gradient Centrifugation?
A
  • it is the separation based on density
  • this is the size and the shape
  • there is an increasing sucrose gradient
  • you can use different forms of sucrose concentration
  • this can help to isolate sub cellular structures
  • the sucrose with the greatest density is always at the bottom of the test tube used for centrifugation
52
Q
  1. What is the Solvent Concentration for Differential Centrifugation?
A
  • there is a stable solvent concentration (gradient)
    (of sucrose)
53
Q
  1. What is the Solvent Concentration for Density Gradient Centrifugation?
A
  • there is a steep solvent gradient
54
Q
  1. What are the Configuration Steps for Differential Centrifugation?
A
  • there are multiple configuration steps
  • they have an increasing acceleration and time
55
Q
  1. What are the Centrifugation steps for Density Gradient Centrifugation?
A
  • there is a single centrifugation step
56
Q
  1. What is the Separation basis for Differential Configuration?
A
  • size
57
Q
  1. What is the Separation Basis for Density Gradient Centrifugation?
A
  • density
  • this is the shape and size

MED 103- BIOLOGY I (53 decks)

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