2 Conditions on early Earth made the origin of life possible Physical and chemical processes on Earth may have produces simple cells on earth.The process of make these cells include:1. Abiotic synthesis of small organic molecules2. Joining of these small molecules into macromolecules3. Packaging of molecules into protocells (Protobiants)4. Origin of self-replicating molecules
3 Synthesis of Organic Compounds Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic. (C02, N2, Hydrogen Sulfide H2S, Sulfur Dioxide S2O)In the 1920s, A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing (Electron-Adding) environment.In 1953, Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possibleMiller-Urey–type experiments demonstrate that organic molecules could have formed with various possible atmospheres
4 Abiotic Synthesis of Macromolecules RNA monomers have been produced spontaneously from simple molecules.Amino acid polymerize when they are concentrated on hot sand, clay, or rock. This proved that is it possible for these molecules to function as a catalyst.
5 ProtocellsReplication and metabolism are key properties of life and may have appeared togetherProtocells may have been fluid-filled vesicles with a membrane-like structureIn water, lipids and other organic molecules can spontaneously form vesicles with a lipid bilayerVesicles exhibit simple reproduction and metabolism and maintain an internal chemical environment
6 an index of vesicle number Figure 25.30.4Precursor molecules plusmontmorillonite clayan index of vesicle numberRelative turbidity,0.2Precursormolecules only204060Time (minutes)(a) Self-assembly1 mVesicleboundaryFigure 25.3 Features of abiotically produced vesicles.20 m(b) Reproduction(c) Absorption of RNA
7 RNA and Self-Replication The first genetic material was probably RNA, not DNARNA molecules called ribozymes have been found to catalyze many different reaction-For example, ribozymes can make complementary copies of short stretches of RNAVesicles with RNA capable of replication would have been protocellsRNA could have provided the template for DNA, a more stable genetic material
8 Origin of Life RecAphttps://www.youtube.com/watch?v=SWY3FKbtEz8