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Cells and the Origin of Cell Theory

Cells and the Origin of Cell Theory. History of the Cell Theory. Before microscopes, belief in supernatural causes of diseases Could not see microorganisms What branch of biology? Cells = basic units of living organisms. Microscopes. Originally a hand lens to view quality of cloth

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Cells and the Origin of Cell Theory

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  1. Cells and the Origin of Cell Theory

  2. History of the Cell Theory • Before microscopes, belief in supernatural causes of diseases • Could not see microorganisms • What branch of biology? • Cells = basic units of living organisms

  3. Microscopes • Originally a hand lens to view quality of cloth • Anton van Leeuwenhoek (mid-1600s) first to examine water under microscope • Credited with development of light microscope

  4. Anton von Leeuwenhoek’s Microscope

  5. Improvements • Compound light microscope- series of lens to magnify objects (1500x) • Robert Hooke used one to observe cork magnified 30x • Observed small geometric shapes • Dubbed these cells (resembled monk rooms)

  6. Hooke’s Microscope

  7. Cell Theory • 1830’s German scientist Matthias Schleiden realized that plants made up of cells • Theodore Schwann made same determination of animals • = Cell Theory

  8. Many resources (including your book) give only credit to Scleiden and Schwann • Original third tenet was spontaneous generation • Rudolph Virchow - "Omnis cellula e cellula”

  9. Cell Theory • All organisms are composed of one or more cells • The cell is the basic unit of organization of organisms • All cells come from preexisting cells

  10. Recent Developments • 1940’s were able to use beam of electrons instead of light • 500 000x • Electron microscope • Scanning Electron Microscope • Transmission Electron Microscope

  11. Scanning Electron Microscope • SEM • Electrons are reflected off the surface of the specimen • 3D shape

  12. http://micro.magnet.fsu.edu/primer/virtual/virtual.html • http://www.mos.org/sln/SEM/gallery.html

  13. Transmission Electron Microscope • TEM • Allows to see inside of cell • Electrons pass through instead of light • http://nobelprize.org/physics/educational/microscopes/tem/

  14. Size Comparison

  15. Prokaryote vs. Eukaryote • With the invention of microscopes, scientists could see two groups of cells • Prokaryotes • Eukaryotes

  16. Prokaryote • 1-10 m in diameter • NO membrane-bound organelles • 1 circular DNA molecule located in nucleoid region

  17. Plasma membrane, cytoplasm & ribosomes • Most have a cell wall (peptidoglycan) • May have a polysaccharide capsule • Ex. bacteria & cyanobacteria

  18. Prokaryotic Cell

  19. Eukaryote • 10-100 m in diameter • Nucleus & other membrane-bound organelles • 2 or more linear DNA molecules located in nucleus • Plasma membrane, cytoplasm & ribosomes some have a cell wall (cellulose or chitin) Ex. plants, animals, fungi, protista

  20. Animal Cell Animal Cell

  21. Plant Cell

  22. QUESTIONS?????

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