Chapter_22_Origin_and_History_of_Life_on_Earth

Chapter_22_Origin_and_History_of_Life_on_Earth - Chapter 22...

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Unformatted text preview: Chapter 22 Origin and History of Life on Earth Universe began with the Big Bang: 13.7 billion yrs ago Supernovas (exploding stars) formed simple molecules of water, carbon monoxide and hydrocarbons 4.6 bya: our solar system was formed Earth is 4.55 billion yrs old 4 billion years ago: earth was cooled enough for oceans to form 4 bya 3.5 bya: emergence of life How? Prior to this class, everyone should have learned: living cells are complex collections of molecules and macromolecules. DNA stores information to AA and protein production RNA acts as the middle man between the information and the production of proteins proteins: foundation for structure and activities of living cells Origin of Life in 4 stages: 1. Nucleotides and amino acids produced (prior to the existence of cells) 2. Nucleotides and amino acids become polymerized to form DNA, RNA, and proteins 3. Polymers become enclosed in membranes 4. Polymers (enclosed in membranes) evolve cellular properties Hypotheses to the Origin of Amino Acids and Nucleotides:- Reducing Atmosphere Hypothesis- Extraterrestrial Hypothesis- Deep-Sea Vent Hypothesis What we do know: originally called primordial soup in 1920s prebiotic soup accumulation of organic molecules under conditions of low oxygen over a long period of time how was the soup created? Reducing Atmosphere Hypothesis: Stanley Miller 1953 Miller and Urey experiment water (boiled) produces water vapor, which rises to a chamber containing H2, CH4 (methane), and NH3 (ammonia) added electrical discharges (lightning) condenser cooled vapor into droplets (precipitation) analyzed droplets Found: Hydrogen cyanide (HCN) and formaldehyde (CH2O) precursors of complex organic molecules also found amino acids, sugars, and nitrogenous bases Extraterrestrial Hypothesis meteor (enters earth atmosphere), meteoroid (floating around in space), meteorite (makes contact) many belong to a class called Carbonaceous Chondrites contain large amounts of organic carbon, including AA and nucleic acid bases however, destroyed in intense heating when large bodies enter the atmosphere? Deep-Sea Vent Hypothesis deep-sea vents: cracks in the Earths surface where superheated water (572deg F) rich in metal ions and Hydrogen sulfide (H2S) mix with cold water Temperature within this gradient are suitable for synthesis of molecules needed to support life Origin of Life in 4 stages: 1. Nucleotides and amino acids produced (prior to the existence of cells) 2. Nucleotides and amino acids become polymerized to form DNA, RNA, and proteins 3. Polymers become enclosed in membranes 4. Polymers (enclosed in membranes) evolve cellular properties Stage 2: _____________________ polymerized to form complex organic polymers (i.e. DNA, RNA, proteins) __________ competes with ____________: experimentally could not occur in water _______: ______ (Mg2+) bind nucleotides to the clay positioning nucleotide in a way that promotes bond formation between phosphate and ribose sugar of an adjacent nucleotide Form RNA Simple Organic Polymers Hydrolysis. Polymerization Clay: Cations Origin of Life in 4 stages:...
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Chapter_22_Origin_and_History_of_Life_on_Earth - Chapter 22...

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