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Lecture 03.docx

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Biological Sciences
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Bebhinn Treanor

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Friday, September, 14 , 2012 BIOAO1- The Origins and Chemical Building Blocks of Life: Lecture 03 Overview:  How were the organic molecules (amino acids, nucleotides) that define life created?  How were these assembled into macromolecules (proteins, nucleic acids)?  How were these able to reproduce themselves?  How were these assembled into a system separated from the surroundings? How did Life on Earth Originate?  4.5 billion years ago  Severe volcanic and tectonic activity  Intense UV energy from the sun  No oxygen until photosynthesis occurred  Basically: NO LIFE EXISTED Origin of Life on Earth:  Chemical and physical processes on earth produced simple cells  It had characteristics of living organisms: It happened in 4 main stages:  Abiotic synthesis of small organic molecules (monomers) - Abiotic is non-living - Synthesized through chemical and physical processes  Polymerization: joining of monomers into polymers  Packaging of these molecules into Protobionts (membrane bound system) that maintained distinct internal chemistry  System to store information and guide synthesis 1. Abiotic Synthesis: All life forms made of macromolecules: -nucleic acids -proteins -lipids -carbohydrates How did these molecules form in the absence of life? Three major hypotheses: 1. Primordial Soup 2. Deep-Sea Vents 3. Extraterrestrial Origins(Panspermia) 1. Primordial Soup:  Atmosphere contained large concentration of molecules rich in electrons, ammonia, methane, hydrogen - (Water vapour, hydrogen, carbon dioxide, ammonia, methane, but no oxygen)  Molecules create reducing atmosphere where molecules can interact  Oparin-Halane hypothesis (1920): proposed the idea that macromolecules were created from this soup  Proof taken from Miller-Urey Experiment (1953) - They simulated atmosphere of primordial earth, took the molecules , put in closed system, provided energy through electrode sparks - Results: Organic compounds (amino acids) have been synthesized - First experiment that synthesized molecules 2. Deep-Sea Vents:  Other scientists didn’t think there was enough ammonia, to make it happen  Hydrothermal vents, send out heated water, which is rich in nitrogen, hydrogen sulphide, hydrogen, carbon dioxide - Bubbles in chambers , and create gradient and make catalytic cells  In these cells everything else is formed (lipids, proteins, nucleotides) 3. Extra-Terrestrial Origins( Panspermia):  More than 500 meteorites impact Earth each year  They are rich in organic molecules  E.g. Murchison meteorite (1969) -Amino acids, glycine, glutamic acid, alanine -Purines and pyrimidines -Some scientists believe that the meteor was filled with these molecules after hitting earth 2. Polymerization:  Components of life are called polymers (chains) -Nucleic acids: polymers of nucleotide
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