Cell Biology Lab2

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Cell Biology Lab-2

• Measurements and Microscopy

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Why the Metric System?

• Its universal the whole world uses it.
• It make sense based on units of ten therefore
  easy to convert units by moving decimal places.
• Its relevant based on actual standards not as
  arbitrary as the old English system.
• The metric system is the standard system for
  science (even American science journals require
  metric measurements!)

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Standard Metric Units

• Length meter
• Weight gram
• Volume liter
• Temperature degrees Centigrade (Celsius)

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Conversions

• Different prefixes for different scale.
• Example centi one hundreth.
• Therefore 1 centi-meter is 1/100 of a meter or
  0.01m.
• Example milli one thousandth.
• Therefore 1 milli-liter is 1/1000 of a liter or
  0.001L.
• Example kilo thousand.
• Therefore 1 kilo-gram is 1,000 grams or 1,000g.

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Length measurements at the cellular and molecular
level (i.e. really small sizes!)

• Still use the meter as the standard.
• However, since we are dealing with very small
  lengths, most commonly used pre-fixes are the
  micro-meter ( one millionth of a meter or
  0.000001m also written as 1µm).
• nano-meter (0.000000001m) or 1nm.
• Ångström unit (0.0000000001m) or 1Å.

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A Word About Temperature

• Celsius or Degrees Centigrade.
• Scaled to the physical properties of H2O.
• Freezing (melting) point is 0 degrees Celsius
  (32o F)
• Boiling point is 100 degrees Celsius (212o F).
• Since pretty much all life on Earth is dependent
  on water and it is known as the universal
  solvent, it makes pretty good since to base the
  temperature scale on waters phyiscal properties!

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Microscopy

• Earliest microscopes were invented in the 1600s.
• Biological cell theory was devised in 1835.
• Electron microscopes were developed in the 1930s.

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Microscope Types

• Stereomicroscope or Dissecting Microscope.
• View entire objects under low magnification in
  3-dimensions. (up to 45x)
• Compound Light Microscope.
• View thinly sliced sections under higher
  magnification using two sets of lenses. (up to
  1,500x)
• Electron Microscope.
• Instead of light, uses stream of electrons to
  see object.
• Highest magnification (up to 100,000x).
• Transmission Electron Microscope
• Thinly sliced sections
• Scanning Electron Microscope.
• 3-dimensional imaging of surface of object.

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Microscope Basic Parts

• Head
• Nose
• Arm
• Base

Always carry a microscope by holding the arm in
one hand and supporting the base with the other.
Never pick-up by head, nose, or stage.
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Microscope Basic Parts

• Lenses ocular lens (eyepiece) objective lens
  (closest to object being viewed usually more
  than one objective lens on a revolving
  nosepiece).
• Adjustment knobs brings object into focus
  coarse-adjustment knob and fine-adjustment knob.
  
• First adjust the coarse adjustment and then use
  the fine adjustment.
• Always start with the lowest-power objective lens
  first.
• With the higher power objective lens(es), only
  use the fine adjustment!

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Microscope Basic Parts

• Stage
• Holds object (slide) being viewed. Adjustment
  knobs (coarse and fine) raise or lower the stage.
• Stage clips hold slide in place on the stage.
• Mechanical stage allows adjustment (left or
  right up or down) of slide in relation to
  objective lens
• Light source.
• Can use a mirror to direct ambient room light or
  have its own built-in light source.
• Condenser directs light to object.
• Diaphragm control amount of light used to view
  the object.

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Microscopy Visual Terms

• Magnification amount object is magnified more
  than viewing with naked eye. Lens usually has
  magnification on it. Total magnification
  occular lens x objective lens.
• Field of View how much of the object you can
  see (usually measured width-wise). As
  magnification increases, field of view decreases.
• Parfocal object pretty much stays in focus as
  you switch lenses. May need fine adjustment.

REMEMBER - Start with low power lens and then
progress to high power
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Slide Preparation

• Stains and dyes.
• Wet mount