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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 • Anton van Leeuwenhoek (mid-1600s) first to examine water under microscope • Credited with development of light microscope Anton von Leeuwenhoek’s Microscope 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) Hooke’s Microscope Cell Theory • 1830’s German scientist Matthias Schleiden realized that plants made up of cells • Theodore Schwann made same determination of animals • = Cell Theory • Many resources (including your book) give only credit to Scleiden and Schwann • Original third tenet was spontaneous generation • Rudolph Virchow - "Omnis cellula e cellula” 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 Recent Developments • 1940’s were able to use beam of electrons instead of light • 500 000x • Electron microscope • Scanning Electron Microscope • Transmission Electron Microscope Scanning Electron Microscope • SEM • Electrons are reflected off the surface of the specimen • 3D shape • http://micro.magnet.fsu.edu/ primer/virtual/virtual.html • http://www.mos.org/sln/SEM /gallery.html Transmission Electron Microscope • TEM • http://nobelpriz e.org/physics/e • Allows to see ducational/micr inside of cell oscopes/tem/ • Electrons pass through instead of light Size Comparison Prokaryote vs. Eukaryote • With the invention of microscopes, scientists could see two groups of cells • Prokaryotes • Eukaryotes Prokaryote • 1-10 m in diameter • NO membrane-bound organelles • 1 circular DNA molecule located in nucleoid region • Plasma membrane, cytoplasm & ribosomes • Most have a cell wall (peptidoglycan) • May have a polysaccharide capsule –Ex. bacteria & cyanobacteria Prokaryotic Cell 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 Animal Cell Anima l Cell Plant Cell QUESTIONS?????
"Origin of Cells and the Cell Theory"