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The Cell Theory

Learn about the history of the cell theory, from Robert Hooke's discovery in 1665 to the modern understanding of cells. Explore the importance of cells in disease research and why they come in different sizes.

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The Cell Theory

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  1. The Cell Theory

  2. Some Random Cell Facts • The average human being is composed of around 100 Trillion individual cells!!! • It would take as many as 50 cells to cover the area of a dot on the letter “i” WOW!!!

  3. Discovery of Cells • 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. • He described the cells as tiny boxes or a honeycomb • He thought that cells only existed in plants and fungi

  4. Anton van Leuwenhoek • 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms • He called them “animalcules” • He also observed blood cells from fish, birds, frogs, dogs, and humans • Therefore, it was known that cells are found in animals as well as plants

  5. 150-200 Year Gap??? • Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made. • This is probably due to the widely accepted, traditional belief in Spontaneous Generation. • Examples: -Mice from dirty clothes/corn husks -Maggots from rotting meat

  6. 19th Century Advancement • Much doubt existed around Spontaneous Generation • Conclusively disproved by Louis Pasteur Pasteur: Ummm, I don’t think so!!! ? = +

  7. Development of Cell Theory • 1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells • 1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.

  8. Development of Cell Theory • 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.

  9. The Cell Theory Complete • The 3 Basic Components of the Cell Theory were now complete: • 1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39) • 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) • 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)

  10. Modern Cell Theory • Modern Cell Theory contains 4 statements, in addition to the original Cell Theory: • The cell contains hereditary information(DNA) which is passed on from cell to cell during cell division. • All cells are basically the same in chemical composition and metabolic activities. • All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc) • Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane)

  11. How Has The Cell Theory Been Used? • The basic discovered truths about cells, listed in the Cell Theory, are the basis for things such as: • Disease/Health/Medical Research and Cures(AIDS, Cancer, Vaccines, Cloning, Stem Cell Research, etc.)

  12. Why Are Cells So Small? It’s all about:Surface Area-to-Volume Ratio Size Matters! Large Cells vs. Small Cells Cell radius (r) 1 unit 10 units Surface area (4╥r2) 12.57 units2 1257 units2 Volume (4/3╥r3) 4.189 units3 4189 units3 ______ ______ SA/V= 2.98 0.30 As a cell get larger, its volume increases at a faster rate than its surface area!

  13. Eukaryote Prokaryote Archaebacteria&Bacteria Classification • Old 5 Kingdom system • Monera, Protists, Plants, Fungi, Animals • New 3 Domain system • reflects a greater understanding of evolution & molecular evidence • Prokaryote: Bacteria • Prokaryote: Archaebacteria • Eukaryotes • Protists • Plants • Fungi • Animals

  14. KingdomBacteria KingdomArchaebacteria KingdomProtist KingdomFungi KingdomPlant KingdomAnimal

  15. Domain Bacteria Domain Archaea Domain Eukarya Common ancestor Prokaryotes Domain Bacteria Domain Archaebacteria

  16. Bacteria live EVERYWHERE! • Bacteria live in all ecosystems • on plants & animals • in plants & animals • in the soil • in depths of the oceans • in extreme cold • in extreme hot • in extreme salt • on the living • on the dead Microbes alwaysfind a way tomake a living!

  17. Bacterial diversity rods and spheres and spirals… Oh My!

  18. eukaryote cell prokaryotecell Prokaryote Structure • Unicellular • bacilli, cocci, spirilli • Size • 1/10 size of eukaryote cell • 1 micron (1um) • Internal structure • no internal compartments • no membrane-bound organelles • only ribosomes • circular chromosome, naked DNA • not wrapped around proteins

  19. Domain Bacteria Domain Archaea Domain Eukarya Common ancestor Eukaryotes Domain Eukarya

  20. eukaryote cell prokaryotecell Eukaryote Structure • Unicellular or Multicellular • Plant, animal, fungi, protist • Size • 10X larger than a prokaryote cell • 10-100 micron (1um) • Internal structure • Far more complex (compartmentalized) • nucleus containing DNA • other membrane-bound organelles • ribosomes (no membrane) • Linear chromosome • wrapped around proteins

  21. Prokaryote vs. Eukaryote Chromosome Prokaryote Eukaryote double helix

  22. mitochondria chloroplast Variations in Cell Interior cyanobacterium(photosythetic) bacterium aerobic bacterium internal membranesfor respirationlike a mitochondrion(cristae) internal membranesfor photosynthesislike a chloroplast(thylakoids)

  23. outer membrane of lipopolysaccharides Gram-negative bacteria Gram-positive bacteria peptide side chains outer membrane cell wall peptidoglycan cell wall peptidoglycan plasma membrane plasma membrane protein Prokaryote Cell Wall Structure That’simportant foryour doctorto know! peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides

  24. Prokaryotic metabolism • How do bacteria acquire their energy & nutrients? • photoautotrophs • photosynthetic bacteria • chemoautotrophs • oxidize inorganic compounds • nitrogen, sulfur, hydrogen… • heterotrophs • live on plant & animal matter • decomposers & pathogens

  25. Genetic variation in bacteria • Mutations • bacteria can reproduce every 20 minutes • binary fission • error rate in copying DNA • 1 in every 200 bacteria has a mutation • you have billions of E. coli in your gut! • lots of mutation potential! • Genetic recombination • bacteria swap genes • plasmids • small supplemental circles of DNA • conjugation • direct transfer of DNA conjugation

  26. Bacteria as pathogens • Disease-causing microbes • plant diseases • wilts, fruit rot, blights • animal diseases • tooth decay, ulcers • anthrax, botulism • plague, leprosy, “flesh-eating” disease • STDs: gonorrhea, chlamydia • typhoid, cholera • TB, pneumonia • lyme disease

  27. Bacteria as beneficial (& necessary) • Life on Earth is dependent on bacteria • decomposers • recycling of nutrients from dead to living • nitrogen fixation • only organisms that can fix N from atmosphere • needed for synthesis of proteins & nucleic acids • plant root nodules • help in digestion (E. coli) • digest cellulose for herbivores • cellulase enzyme • produce vitamins K & B12 for humans • produce foods & medicines • from yogurt to insulin

  28. How big are cells? • Microscopic (mostly) • Measured in microns µm • (micrometers). • A µm is one millionth of a meter = • 10-9 m = one thousandth of 1 mm.

  29. How big are cells? Smallest free-living cell = Mycoplasma genitalium Size = 0.2 to 0.3 µm

  30. How big are cells? • Bacteria e.g. Eschericia coli (aka E.coli) • Size=1 µm by 3 µm

  31. How big are cells? • Human red blood cell = 8 µm in diameter

  32. How big are cells? • Largest cell on the human body = ovum • Size= • 1000 µm in diameter (1 mm)

  33. How big are cells? • Smallest cell in the human body = sperm cell.

  34. How big are cells? • Largest cell with a metabolism = Chaos chaos Size=1-5 mm in length. common name = Giant Amoeba Chaos diffluens, is an amoeba closely related to the giantamoebae

  35. How big are cells? • Largest cell = yolk of an ostrich egg

  36. Ostrich, egg, humans

  37. Ostrich emerged from egg

  38. How can we study cells? Problem: They are microscopic! Solution: Use a microscope!

  39. Types of Microscopes • Compound light microscope • Light passes through lenses to magnify image up to 1000X • Can observe living cells

  40. Types of Microscopes 2. Electron microscope • Uses a beam of electrons to magnify image > 1000X • Kills cells being observed

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