The Origin of Cells
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| When did life begin? | -Earth is 4.5 billion years old
-It took approx .5 billion years for the Earth to cool to form a crust
-As early as 4 billion years ago early cells existed
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| Cell Theory questioned in the origin of cells | -All cells come from pre-existing cells
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| The four/five steps in creating the first cells (Step One) | 1. The non-living synthesis of simple organic molecules from a mixture of any three of methane, hydrogen, ammonia and water vapor.
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| The four/five steps in creating the first cells (Step Two) | 2. The assembly of these molecules into polymers
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| The four/five steps in creating the first cells (Step Three) | 3. The origin of self-replicating molecules that make inheritance possible
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| The four/five steps in creating the first cells (Step Four) | 4. The packaging of these molecules into membranes with an internal chemistry different from their surroundings.
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| The four/five steps in creating the first cells (Step Five) | 5. The development of binary fission of these protocells.
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| Symbiosis | An association between two or more species.
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| Endosymbiosis theory (Eukaryotes are formed from prokaryotes) | -Mitochondria of eukaryotes came from aerobic bacteria
-Chloroplasts evolved from primitive autotrophic prokaryotes
-Both were taken into larger heterotrophic cells by endocytosis
-Eukaryotes then formed membranes that could contain the prokayotes
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| Evidence to Endosymbiosis Theory | -Mitochondria and chloroplasts have DNA that is separate from the cells nuclear DNA
-This DNA is similar to prokaryotic DNA (not associated with proteins)
-Mitochondria and chloroplasts have small 70S ribosomes (regular eukaryotic ribosomes are 80S)
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| Evidence to Endosymbiosis Theory- Part 2 | -Mitochondria and chloroplasts have double membrane
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| Prior to Louis Pasteur (1822-1895) | -Notion of spontaneous generation was commonly accepted
-This proposed that life is continuously being spontaneously created where no life previously existed
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| Louis Pasteur's Experiment Step One | -Started with two flasks and a nutrient broth in each
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| Louis Pasteur's Experiment Step Two | -Bent the necks of the flasks into "S" shapes
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| Louis Pasteur's Experiment Step Three | -Boiled the broth to kill any existing microbes
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| Louis Pasteur's Experiment Step Four | -Broke off the swan neck from the 1st flask only, exposing the nutrient broth to air from above.
-In flask 2, dust particles remained near the tip of the swan neck
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| Louis Pasteur's Experiment Step Five | -The broth in the broken flask quickly became cloudy (a sign of microbial life)
-The unbroken flask remained clear
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