Microscopes and Cell Models Flashcards
Smallest functional unit of life.
Cell
- 1665
- 1st to see dead cells
- had microscope around 30X magnification
Robert Hooke
- 1670s
- made his own glass lens
- microscope (which wasn’t a compound microscope) could maybe get up to 200X (SEE NOTES FOR DIAGRAM)
- 1st to see living cells
Antoni van Leeuwenhoek
Cell Theory: Schleiden and Schwann 1839
-Has three main parts that are:
- All organisms consist of 1 or many cells.
- The cell is the basic unit of structure for all organisms.
- All cells come from pre-existing cells.
Eduard Strasburger and his “time-lapse” observations in 1880
He could track mitosis in plant cells
Goal is to decipher underlying principles that govern the structure and activity of the cell.
Microscopy
Two powers of microscopy:
- Magnification
- lens (4x,10x,40x) and eye piece (4x, 10x) - Resolution
Ability to make an object appear larger.
Magnification
Ability to distinguish two objects from each other (as being separate).
Resolution
Resolution
d=(0.5*wavelength)/n sin(theta)
d=distance
nsin(theta)=numerical aperture
Resolution Cont…
-The # found on the lens on the microscope.
-n sin(theta)
n=refractive index of the medium you’re using (ex. air, n=1; oil, n=1.5; H2O, n=1.3)
(theta)=1/2 angle of cone light (SEE NOTES FOR DIAGRAM)
Numerical aperture
To increase resolution, what parameters would you change when d=(0.5*wavelength)/n sin(theta)?
-Remember, smaller distance = greater resolution!
- Shorten wavelength (smaller numerator = smaller distance)
- Change n (larger denominator = smaller distance)
- Change cone of light by bringing objective closer to specimen (larger denominator = smaller distance)
- Can see dead or alive cells
- light path is at the bottom
- Ocular lens (eye piece) usually 10x
- Objective: 10x, 40x, 100x
- Condenser (no magnification)
Light microscopy
Focuses light to a single area.
Condenser on microscope
Stained light micrographs
- Staining kills specimen (fixing and staining procedures)
- There are controls in case staining makes something funny happen.
Variations of light microscopy to view living cells
- Bright-field
- Phase contrast
- Differential interference contrast (DIC)
Basic light microscopy
Bright-field
Can make shadows, give more topography of cell, and takes advantage of refractive indexes to cast shadows.
Phase contrast
Shines light both below and on the side of specimen.
Differential interference contrast (DIC)
Excitation and Emission
Fluorescence Microscopy
Microscopy that requires one wavelength to excite sample and another wavelength to emit light.
- Need fluorescence molecules (most common is GFP)
- Good magnification, but poor resolution
Fluorescence Microscopy (SEE NOTES FOR DIAGRAM)
Microscopy that uses a laser at a particular wavelength that will excite a sample (is a modification of florescence microscopy)
-Sample will emit light through the eye piece
Confocal microscopy
Can focus on a particular plane of view, because it blocks out some of the light.
Pin Hole Aperture
Moves to be able to look from layer to layer of specimen.
Motorized stage
