Class Topics

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Microscopes

• Simple light microscope
• One lens
• Living or dead specimen
• Compound light microscope
• more than one lens
• resolution is a problem
• Must be transparent
• (very thin)
• Living or dead specimen

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Microscopes

• Electron microscopes - use a beam of electrons
  (dead specimen)
• Transmission (TEM)- electrons pass through - very
  thin specimen
• Scanning (SEM)- electrons bounce off and get an
  image from the outside
• Like a photo
• Scanning tunneling
• Uses a microprobe
• Can be used on living or dead organisms
• View atoms or molecules

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Magnifications

• Simple light 5-25x
• Compound light 2000x
• Electron microscopes
• SEM 200,000x
• TEM 2,000,000x
• Scanning tunneling 1,000,000,000x

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Microscope

• Adjustment used with high power?
• Purpose of diaphragm?
• Scanning electron vs transmission electron?
• Advantage/disadvantage of CLM?
• How do you carry a microscope?

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Scientists

• Robert Hooke (English, 1665)
• Looked at cork and named cells - after rooms in a
  monastery
• thought only plants had cells
• Anton van Leeuwenhoek (Dutch, 1674)
• First to use microscope to observe living cells
• Father of microbiology
• looked at pond water - animacules (little
  animals)
• ...I could exceedingly plainly perceive it to be
  all perforated and porous, much like a
  Honeycomb...these pores or cells , were not very
  deep, but consisted of a great many little
  boxes... Hooke describing his observations on a
  thin slice of cork.

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Cell Theory

• Matthias Schleiden (1838)
• All plants are made of cells
• Theodore Schwann (1839)
• All animals are made of cells
• Rudolf Virchow (1858)
• All cells come from preexisting cells
• Cells reproduce

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Cell Theory

• All living things are composed of one or more
  cells.
• Cells are the basic units of structure and
  function in living things.
• All cells come from preexisting cells.

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Cell Size

• Most organisms have many small cells rather than
  fewer large ones
• Why?
• Surface area-to-volume ratio
• 61 good
• 31 very large for cells
• Any lower than this is very dangerous
• Allows transfer of materials in and out of cell
  easily
• Cell size small, SAVol high
• Cell size large, SAVol low