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Life 1 – Origins and Chemistry.docx

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Natural Science
NATS 1840
Carl Wolfe

Life 1 – Origins and Chemistry Chapter 15 - section 1, 2 & 4 In the Beginning.. The planets formed from the same cloud of gas and dust which gave birth to the Sun, about 4, 6 billion years ago.. Being made of the same stuff, the terrestrial planets likely looked very similar to one another at first. The Earth has changed significantly since. But current conditions on Mars and Venus suggest what the primordial Earth might have been like. Primordial Atmosphere: Earth’s original atmosphere probably looked a lot like those of Venus and Mars do today. The gases likely to have been present include: - Carbon Dioxide (CO2) - Water (H2O) - Methane - Ammonia - Hydrogen Sulfied - Hydrochloric Acid - Molecular Hydrogen - Notice the absence of Oxygen Origins of Life: Every culture has a creation myth based on ancient myths, beliefs, and/or faith. The accepted scientific view of our origins begins with the conditions on the newly-formed planed Earth. The early environment likely featured - An unpleasant atmosphere: - Lots of ultra-violet (UV) Urey Miller Experiment (1952): To reproduce the conditions believed to have existed on the Earth after its outer curst had solidified - H2, H2O, NH3, CH4 were combined in a flash: - Electrical sparks in the flask simulated lightning. After one week the flask contained a reddish brown muck. This substance was found to contain - Hydrocarbons - Amino Acids (2%) Amino acids are the building blocks of all known proteins. Urey- Miller (Cont’d) The experiment demonstrated that - Organic molecules could be synthesized from inorganic ingredients without the presence of life: - Amino acids appear readily in the process Our understanding of the Earth’s primordial environment has changed since 1952. But the fundamental conclusion of the Urey Miller experiment has withstood the test of time. Life was likely a natural outcome of the conditions which prevailed on Earth 4 billion years ago. Chemical Evolution The first billion years witnessed slow but steady chemical evolution. However, exactly how increasingly complex organic molecules combined to form living organisms is not known. The ‘clumping” hypothesis process that increasingly large assemblies of organic molecules formed at random. Those ‘clumps’ which were most adapt at processing matter and energy became the first photocells. But a prof of principle experiment is still awaited… Chemical Basis of Life: All known life forms are built up from organic molecules Many of the organic molecules involved are gigantic. Such macromolecules involve thousands of atoms and cone in four main types: - Proteins - Nuclear Acids (DNA, RNA) - Carbohydrates (sugars) - Lipids (fats) All are polymers made up of chains of simpler molecules called monomers. Proteins: Macromolecules composed of one or more polypeptides folded into a uniq
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