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Origin of Life on Earth


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Origin of Life on Earth

  1. 1. Origin of Life on Earth<br />Chapter 22<br />Section 1<br />
  2. 2. Important Molecules of Life<br />DNA<br />Stores genetic material<br />RNA<br />Protein synthesis and other important roles<br />Proteins<br />Structure and activity of the cell<br />
  3. 3. How they came to be . . .<br />The origin of life occurred in four stages<br />Stage 1 – Organic molecules were produced before cells existed<br />Stage 2 – Polymerization of organic molecules formed polymers<br />Stage 3 – Polymers became enclosed in membranes<br />Stage 4 – Membrane bound polymers acquired cellular properties<br />
  4. 4. Stage 1<br />Nucleotides and amino acids were created before the existence of cells<br />It is hypothesized that these organic molecules formed spontaneously due to the conditions of early Earth<br />The molecules formed a prebiotic soup<br />
  5. 5. Reducing Atmosphere Hypothesis<br />Early Earth had a reducing atmosphere<br />Lacked oxygen<br />Abundance in water vapor, hydrogen gas, methane, and ammonia<br />Miller and Urey experiment<br />
  6. 6. Extraterrestrial Hypothesis<br />Meteorites, landing on early Earth, were abundant with organic molecules<br />
  7. 7. Deep-Sea Vent Hypothesis<br />Cracks in the Earth’s surface releases hot water<br />The mixture of the hot water and the cold sea water created a gradient suitable for the formation of organic molecules<br />
  8. 8. Stage 2<br />Nucleotides and amino acids were polymerized to form RNA/DNA and proteins<br />Polymerization took place on clay<br />Could not take place in water because hydrolysis would compete with polymerization<br />Clay can catalyze reactions<br />
  9. 9. Stage 3<br />Droplets of organic material<br />Surrounded by a ring of water molecules <br />Vesicles with a phospholipid membrane<br />Coacervate<br />Liposome<br />
  10. 10. Stage 4<br />Polymers underwent mutations that changed their function<br />Chemical Selection<br />Polymers that had functions that were beneficial, were increased<br />
  11. 11. RNA World<br />It is hypothesized that the world used to be an RNA world<br />RNA’s Key functions<br />Information storage<br />Enzymatic activities<br />Self-replication<br />RNA underwent mutations<br />New functions<br />
  12. 12. RNA DNA/RNA/Protein<br />Information Storage<br />DNA took up RNA’s ability to store information<br />Reduced the roles of RNA<br />DNA was created through reverse transcription<br />Cellular Functions<br />Proteins took up the function of catalyst and others<br />Proteins were formed due to RNA’s ability to catalyze the formation of peptide binds<br />