1. PTYS 214 – Spring 2011  Homework #2 DUE in class TODAY  Homework #3 available for download on the class website DUE Thursday, Feb. 3  Useful Reading: class website  “Reading Material” http://en.wikipedia.org/wiki/Origin_of_life http://www.talkorigins.org/faqs/abioprob/originoflife.html http://sandwalk.blogspot.com/2009/05/metabolism-first-and-origin- of-life.html Announcements

2. Homework #1  Total Students: 29  Class Average: 7.5  Low: 4  High: 10 If you have questions see Lissa

4. Metabolism-first vs. Replication-first  Both theories have a problem with low probability events: –Metabolism-first: bringing together the right sets of metabolic paths in an enclosed setting –Replication-first: bringing together a self-replicating polymer  Neither has been reproduced in the laboratory Some new results: Feb. 2009: “Self-sustained replication of an RNA enzyme”, Lincoln and Joyce, Science 323, p. 1229 Open (lively!) debate

5. Bottom-Up Strategy: Primordial Soup Theory Life began in a warm pond/ocean from a combination of basic building blocks of life (organic molecules) into ever more complex organic molecules, such as amino acids, proteins, and some early version of RNA Where did the building blocks of life came from?

6. Building Blocks of Life: Atmosphere  Almost all organic carbon which we observe today is produced biologically (via photosynthesis): CO 2 + H 2 O  CH 2 O + O 2 (CH 2 O – any organic matter)  Carbon which comes out of volcanoes is in a form of CO 2  CO 2 gas mixture does not produce organic molecules on its own inorganic organic

7. Recipe for a Primordial Soup Find it on YouTube at: http://www.youtube.com/watch?v=7pt0rIZ3ZNE

8. CH 4 NH 3 H 2 O CHNOCHNO HCN (cyanide) H 2 CO (fomadehyde) Amino acids Other simple organics Spark discharge breaks the chemical bonds in CH 4, NH 3, H 2 O C, H, N, O atoms can recombine into various organic molecules that eventually end up into the oceans Urey-Miller Experiment in Short Ancient atmosphere

9. Problems of organic synthesis via Urey-Miller experiment  It is hard to justify large amounts of NH 3 and CH 4 in the early (prebiotic) atmosphere  In a CO 2 -rich atmosphere organic production by spark discharge is not very efficient – dilution problem  If CH 4 /CO 2 < 0.1 essentially no organic production

10. CO NO NO 2 H 2 O O >> C,N,H CO 2 >> CH 4, NH 3 In an atmosphere dominated by CO 2 the most abundant radical after spark discharge or photolysis is O “Bad” CO 2 Atmosphere The dominant species after recombination are inorganic molecules! Current Research: organic production in CO 2 -N 2 -H 2 mixtures

11. Building Block of Life: Hydrothermal Vents Find it on YouTube: http://www.youtube.com/watch?v=D69hGvCsWgA

12. Organic synthesis in Hydrothermal Vents  Hydrothermal vents were likely to be present in the prebiotic environment  Synthesis requires only CO 2, H 2 O and silicate rocks  Processes Involved (Fischer-Tropsch - high T and P)  Serpentinization:  Spinel polymerization: Olivine +  Serpentine + Magnetite (spinel group) Seawater & dissolved CO 2 Hematite

13. Major hydrothermal vent sites © Dr. Sven Peterson – IFM-GEOPMAR, Keil

14. Problems with organic synthesis via Hydrothermal Vents  Only very simple organics are generated (no amino acids, etc.)  Any complex organics are unstable at high temperatures (they are not around long enough to form larger macromolecules)

15. Hydrothermal Vents: Organics are unstable at high temperatures 1) Organic molecules could form away from vents, where temperatures are lower (it is a steep gradient!) 2) Expandable clay (smectites) surrounding the hydrothermal vents might serve as a “primordial womb" for infant organic molecules, sheltering them within its mineral layers Williams et al. (2005) Geoloby 33, p. 913

16. Can you think of any other source of organic matter? Both atmosphere and hydrothermal vents have problems producing complex organics Space! Extraterrestrial origin – organic material was synthesized in space and was brought to Earth somehow

17. ~150 interstellar and circumstellar molecules H2H2 CH 2 C6H6C6H6 NH 3 Glycine

18. Giant molecular cloud Star formation

19. Do we have examples of extraterrestrial material on Earth? Meteorites! Murchison (1969, Australia)

20. Meteorites Natural objects originating in outer space that survive an impact with the Earth's surface without being destroyed  Chondrites – 86% ( oldest rocks in the solar system) 5% are Carbonaceous Chondrites  Achondrites – 8%  Irons – 5%

21. Some of the amino acids synthesized in the Miller-Urey experiment and also found in the Murchison meteorite

22. Problems with Extraterrestrial Organic Delivery  Simple organics only – no large macromolecules  It is hard to accumulate necessary mass of carbon for the “concentrated” prebiotic soup (dilution problem)

23. Building Blocks or Life: The Phosphorus Problem CosmicDNA H2.8 × 10 6 10 O14006 C6809.5 N2303.75 S430 P11 Phosphorus is a very rare element in the universe On Earth it is found as insoluble phosphate minerals Life selects phosphorus!

24. Phosphorous is in nucleic acids (DNA,RNA) (like phospholipids and ATP) …and other important organic macromolecules

25. Extraterrestrial P Two forms: –Phosphate Ca 5 (PO 4 ) 3 (OH,F) like typical phosphates on Earth –Schreibersite (Fe,Ni) 3 P NOT a naturally- occurring crustal mineral Seymchan meteorite (pallasite) 20 cm

26. Phosphorus on the Earth’s surface  Phospates are not soluble in water at normal terrestrial conditions  Schreibersite rusts in presence of water to form soluble and reactive P Meteorites may be an important source of P for the origin of life Pasek (2008) “Rethinking early Earth phosphorus geochemistry” PNAS 105(3), p.853

27. Bottom-Up Approach - Summary 1. Small organic molecules Small organic carbon molecules could have come from three sources in the prebiotic world: 1)Synthesis in the atmosphere 2)Synthesis in the hydrothermal vents 3) Synthesis in space and delivery via meteorites

28. Bottom-Up Approach - Summary 2. Subunits of RNA Phosphates: rock (meteorite) weathering Ribose: CO 2 + H 2 O + Energy  5 CH 2 O + H 2 O  Ribose Base: CH 4 + N 2 + Energy  5 HCN  Adenine (formaldehyde) (and similar reactions for the other 3 RNA bases) (hydrogen cyanide)

29. - Formation of longer molecules from simple organic molecules Dehydration reaction: two simpler organic molecules are bonded through the loss of water Bottom-Up Approach - Summary 3. Polymerization H2OH2O

30. Primordial soup was probably too dilute in simple monomers to form very long molecules Possible concentration mechanisms:  Heat from expelled lavas (eg. St. Helens)  Tidal pools (evaporation)  Freezing water  Mineral catalysts (clays) All of them are quite inefficient compared to enzymes and cells The Dilution Problem

31. Minerals can help polymerization Minerals (like clay and pyrite) can provide a repeating pattern to act as a template for polymerization  Small organic molecules could have stuck to the mineral surface (organic film) Kaolinite

32. Quiz Time !