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Systems Microbiolo46 - ° This early atmosphere had mildly...

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Systems Microbiology • Life on Earth: How did we (everything) get here? (Lessons in geobiological engineering). o Microbes seem to have originated about 3.8 billion years ago. o But it turns out that the oldest rocks on Earth are only about 4 billion years old (existing in Greenland, Australia, and South Africa). o Slide: “The Early Earth System,” “The Evidence” o It’s hard to make all these inferences, because the earth looks so different now 􀂃 The early earth had no oxygen, water only as steam, and lots of asteroid collisions. o The origin of life on Earth: 􀂃 In situ (originating here) or panspermia (coming from elsewhere via a collision) • Panspermia seems unlikely, though interesting, because outer space can destroy these organic molecules very quickly. 􀂃 The Oparin ocean scenario, or hydrothermal vents? o Determining the atmospheric composition of the early earth is still largely guesswork
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Unformatted text preview: ° This early atmosphere had mildly reducing conditions ° As the earth cooled, H 2 0 dropped from the sky, and the oceans formed. These early oceans contained lots of sulfates and acids. • Some scenarios for the origin of life: o The Miller Urey experiment: CH 4 , H 2 , NH 4 , and H 2 O, plus energy, will generate amino acids and simple sugars. o But how do you produce molecules that actually replicate? ° Slide: ribosomal RNA – its folding, tertiary structure allows it to act as an enzyme: ribozyme. ° Thus we have a single molecule that can reproduce itself and act as an enzyme, and hence this might be where life originated ° There’s also a clay that can create lipids, and once one of these ribozymes ended up inside one of these lipid vesicles, very interesting things could happen. ° However, there are some problems – we don’t really know – this is all speculative....
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