Origin & Ultrastructure

• Spontaneous Generation


  Living organisms arising from non-living matter
• Pre-existing cells


  Cells divide to form new cells
• Robert Remak made the conclusion that cells divide to form new cells


  1852
• Robert Virchow proposed the phrase "omnis cellula e cellula" (all cells come from cells)


  1855
• Prior to these announcements, it was believed that life arose spontaneously from non-living matter
• Reasons for belief in spontaneous generation

  • Lack of technology - microscopes were not extensively used
  • Observations being made - Aristotle observing insects forming from dew or van Helmont observing a mouse appearing from a jar
  • The idea supporting the cultural and religious beliefs of the time

  
• Experiments disproving spontaneous generation

  1. Francesco Redi's maggot and rotting meat experiment

  2. Louis Pasteur's swan-neck flask experiment

  
• Louis Pasteur's experiments


  Designed to verify the principle that cells can only come from pre-existing cells

  
• Louis Pasteur's swan-neck flask experiment


  1. Used swan-neck flasks to trap microorganisms in the bend of the neck

  2. Added nutrient broth, boiled to sterilize

  3. Broke off necks of some flasks

  4. Observed broth in flasks with snapped necks went cloudy, while swan-neck flasks remained clear
• Oparin-Haldine hypothesis


  Four stages to create the original first cells from non-living material: 1) Synthesis of simple organic compounds from inorganic molecules, 2) Assembly into polymers, 3) Development of self-replicating polymers (likely RNA), 4) Formation of lipid membranes to create packages with internal chemistry different from surroundings
• Miller-Urey experiment


  Boiled water to produce steam, mixed with gases (methane, hydrogen, ammonia) to recreate early atmosphere, added electrical discharges to simulate lightning, cooled mixture and found traces of simple organic molecules including amino acids
• Endosymbiosis


  One organism living within another, where the engulfed organism is not digested if the relationship is beneficial
• Endosymbiotic theory

  Theory used to explain the origin of eukaryotic cells, based on the structure of mitochondria and chloroplasts