Study guide geology exam 2

Study guide geology exam 2 - Kristens notes Exam 2 The...

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Kristen’s notes – Exam 2 The emergence of life - Basic unit of life is the cell - Cells contain DNA, RNA, and Proteins - Basic building blocks for DNA, RNA, and Proteins are amino acids - Amino acids contain 5 basic elements C arbon, H ydrogen, O xygen, N itrogen, and S ulfur – CHONS What kind of atmosphere is needed for amino acids to form? - An atmosphere that contains CHONS. - An oxidizing atmosphere An atmosphere with lots of free oxygen (free oxygen = O 2 = breathable oxygen) Today’s atmosphere No Amino acids do not form in the presence of a lot of oxygen Alexander Oparin - A reducing atmosphere An atmosphere with no free oxygen The Earth’s primary atmosphere Earth’s first atmosphere which was captured during the formation of the planet Would contain mainly methane (CH 4 ), CO 2 , ammonia (NH 3 ), and water vapor. Oparin-Haldane hypothesis The Miller-Urey experiment was preformed with a reducing atmosphere and many different kinds of amino acids were formed in a relatively short time. Is this the atmosphere under which amino acids were formed? No If the atmosphere was a primary atmosphere then its composition would be similar to that of the sun. The ratio of Neon-20 to Argon-36 ( 20 Ne/ 36 Ar) on the sun is 30 whereas on Earth the ratio is 0.3. This means that Neon has escaped Earth’s atmosphere much more then it has escaped the Sun’s. The ratio of Nitrogen to Neon (N/Ne) on the sun is 1 which means that there is as much N as there is Ne. However, on Earth N is 86,000 times more abundant than Ne. This means that Ne was lost from our atmosphere and N was added! - A neutral atmosphere Neither oxidizing nor reducing Secondary atmosphere
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Contained very little free oxygen (< 1 % of the O in today’s atmosphere), no NH 3 and contained mainly N 2 and CO 2 William Rubey, -Berkner and Marshall, -Owen, Cess, and Ramanathan Is this the atmosphere under which amino acids were formed? Probably, yes! Problems with a neutral atmosphere The Miller-Urey experiment was preformed with a neutral atmosphere and few amino acids were produced and it took longer. How was so much Nitrogen added to the atmosphere?
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This note was uploaded on 11/16/2010 for the course GEOL 342 taught by Professor Staff during the Fall '08 term at Maryland.

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Study guide geology exam 2 - Kristens notes Exam 2 The...

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