L03_2009 Simple beginnings-1 - “FROM SO SIMPLE A...

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Unformatted text preview: “FROM SO SIMPLE A BEGINNING...” CHEMISTRY AND THE ORIGIN OF LIFE Lecture 03 Cole Gilbert September 2, 2009 1 1 1 / 23 4 . . ! . QuickTime™ and a decompressor are needed to see this picture. ! " # #" ' ( ) )% *( ./ 0 $ ( , %#$ & + Wednesday, September 2nd 4:00 PM - 5:30 PM Stimson Hall Biology Open House LOST & FOUND Lecture: Any personal belongings left behind after lecture will be taken to the Introductory Biology course office in Comstock 1140. Contact Dr. Sarvary [MAS245@cornell.edu] to see if we found your cell phone, clicker, etc. Campus lost and found is at the Cornell Police station in the back of Barton Hall Lab: Personal belongings left in lab may also be picked up at the Introductory Biology course office in Comstock 1140. Meet Biology Faculty Meet Representatives From Cornell Clubs: Pre-med/Pre-vet Organizations Undergraduate Society for Neuroscience Bioethics Society of Cornell And many more Meet Student Advisors who can help you plan for Research and Grad, Med &Vet school Join us, explore bio and eat PIZZA!!! Scheduling a make-up prelim Exam conflicts: If you must miss the prelim due to a conflict with another exam or university-sponsored event (athletics, for example) that is scheduled at the same time as our exam, we will need a note signed on Cornell letterhead by the professor or course coordinator stating : your involvement in the conflicting event the time and date of the event (there isn’t a specific form). your name, net id and Cornell ID This letter must be turned in to Mark Sarvary or to the Course Office (1140 Comstock Hall) one week before the biology prelim. Medical reasons: Persons having a prolonged illness who wish to take a biology make-up exam must obtain a note from their doctor or sign a release authorization form at Gannett Clinic and have copies of their “Office Notes” either mailed or hand-carried to our course office. The form that Gannett Clinic gives patients, which says “This is not an excuse” is not sufficient to document an illness. Concepts and terms artificial selection ATP breeding true codon Francis Collins Darwin deductive reasoning descent with modification differential reproduction Dobzhansky extant falsifiability heritability hypothetico-deductive method inductive reasoning Linneaus natural selection nested sets of similarity taxonomy tree of life unity of life variation vestigial structures “FROM SO SIMPLE A BEGINNING...” CHEMISTRY AND THE ORIGIN OF LIFE Lecture 03 Cole Gilbert September 2, 2009 In the beginning God created the heaven and the earth. Genesis 1:1 Who painted this painting ? A. B. C. D. E. Da Vinci Caravaggio Michelangelo Titian Modigliani Any Scientific Theory of Origin of life... By nature, speculative. Must be consistent with the laws of chemistry and physics. Must explain:. • The process by which the first organic molecules could appear. • The reason why this process does not operate now, but did once. • How a molecule could replicate itself (the first “replicator”). • How a molecule could evolve, including origin of variation natural selection Stars and planets being formed. Photo of Orion Nebula from Hubble Telescope Where we’re going 1. Dating the early Earth 2. Creating organic molecules 3. The RNA World Acasta gneiss 4.03 by Earth’s oldest rocks Isua sediments 3.8 by Rocks older than 3.5 billion years (by) inferred actual Jack Hills zircons 4.4 by by = billion years ago, sometimes also designated as Ga = Giganna Zircon crystals from sediments in Jack Hills, Western Australia How rocks are dated: Potassium –Argon (40K:40Ar) (19p, 21n) Lead –Uranium dating: Oldest is 4.404 billion years. (18p, 22n) 50 m of different zircon crystals How old are the oldest fossils of life on Earth ? Stromatolites from W. Australia Layered mats of cyanobacteria (“blue-green algae”) that trap sediment Fossil stromatolites have a similar gross appearance W. Australia Saratoga Springs, NY Saratoga Springs, NY Oldest fossil stromatolites dated at 3.43 by thin sections reveal cellular elements resembling extant cyanobacteria 10 m Sliced fossil stromatolite reveals layers Thus, 1 by from oldest zircon to cellular life Which of the following radiometric dating elements would be most useful for estimating age of the oldest rocks on Earth? A. B. C. D. E. Radium 226 Rubidium 87 Plutonium 239 Potassium 40 Carbon 14 (half life = 1600 years) (half life = 48.8 billion years) (half life = 24,110 years) (half life = 1.25 billion years) (half life = 5,730 yrs) Stanley Miller + Harold Urey Experimental creation of organic molecules from abiotic precursors Harold Urey Nobel Prize 1934 for work on isotopes, discovery of ‘heavy’ Hydrogen Stanley Miller 1953 Miller – Urey experiment, 1953 Atmosphere: Methane CH4 Ammonia NH3 water vapor H2O Hydrogen H2 Water Spark Heat Abiotic Synthesis of a Primordial “Soup” Abiotic synthesis of: Hydrogen cyanide, Formaldehyde, other aldehydes. Simple organic acids, including amino acids. Check out the website: http://www.ucsd.tv/miller-urey/ And More Synthetic Molecules… amino acids (D and L) Polymerization forms larger molecules Sugars: polymers of formaldehyde (form spontaneously). several sugars (D and L) Some of which are larger N.B. Deoxyribose sugars not formed nucleotide bases Polymerization forms larger molecules Nitrogenous bases: formed from cyanide In the presence of PO4, and Adenine Adenine. Ribose + PO4 Cyclic AMP ATP NADox and NADred Acetyl-Coenzyme A , a purine also, synthesis of Uracil , a pyrimidine Atmospheric considerations Miller’s atmosphere (methane, ammonia & hydrogen) was a reducing atmosphere in which organic molecules are stable. Oxidizing atmospheres destroy (oxidize) organic molecules, but there is scant evidence of free oxygen before about 3 billion years ago. However, current data indicate that early atmosphere may have contained less methane and ammonia, but more carbon dioxide and nitrogen. Thus, it was only weakly reducing or neutral. Some experiments still produce organic compounds. RNA WORLD HYPOTHESIS: The first replicating molecule was probably RNA 1. RNA can self-replicate, although there are errors. 2. RNA can catalyze other chemical reactions. W hy the first self-replicating molecule was probably not DNA • Although self replicating, DNA replication requires enzymes (protein) • DNA not typically a catalyst. • DNA is more stable (lack of –OH at 2’ position is less reactive) How RNA Self Replicates Nucleotides free in solution spontaneously polymerize Once polymerized, additional nucleotides pair up with weak hydrogen bonds Complement sequence serves to reform original sequence. AU u Thomas Cech RNA is also a Catalyst Discovered by Thomas Cech (Colorado) Sidney Altman (Yale) [Nobel in 1989] Sidney Altman Ribozyme Functions in Modern Cells 1) Removal of introns 2) RNA replication 3) RNA elongation 4) Coding for proteins (tRNA) 5) Binding of a.a. to specific tRNA’s 6) Translation (107 x faster than spontaneous) Since then, more than 500 different examples of “ribozymes” discovered. Origin of ribosomes, shared by all living organisms RNA in the Primordial Soup Self-replication Catalysis Families of similar RNAs produced Errors occur, variation arises Molecular evolution RNA WORLD RNA evolves as catalyst to synthesize protein Proteins help the RNA replicate more efficiently Also make double stranded RNA, eventually this becomes DNA DNA takes over. Questions about the origin of life - 1 Why doesn’t new life continue to arise spontaneously? Oxygen: a by-product of photosynthesis started before 3.0 by, creating an oxidizing atmosphere. Organic precursor molecules then unstable Competition: organic precursors are used up. Questions about the origin of life - 2 Was there only one origin of life or were there lots of them ? Most parsimonius answer is one, evidence is the biochemical unity of life: -- All amino acids are L, not D. -- All ribose sugars are D, not L. -- only 20 a.a. used (out of many produced) -- universal genetic code -- universal use of ATP as an energy molecule. UP NEXT Biological macromolecules Energy: lipids & carbohydrates ...
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This note was uploaded on 03/13/2010 for the course BIOG 1101 taught by Professor N/a during the Fall '10 term at Cornell University (Engineering School).

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