219 problem organic building blocks dissolved in

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219 - Problem: organic building blocks dissolved in water will break down by hydrolysis. How do these basic units assemble into polymers? - Solution? In the lab, researchers can assemble polymers up to 50 nucleotides long (and a.a. chains up to 55 a.a. long) by adding clay to a “prebiotic soup” of biological molecules. The clay acts as a catalyst Where did biological polymers come from? - Does this prove the polymers were assembled on clay?
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The Chemical Theory (Oparin-Haldane theory) Inorganic molecules Organic molecules Biological polymers Replicating systems Protocells True cells For natural selection to work: 1. Some action needs to be performed = Phenotype 2. There needs to be replication = Genotype Where did replicating systems come from? RNA world 1982: Discovery that RNA possesses catalytic activity (= speeds up the rate of chemical reactions without itself being consumed) DNA Deoxyribonucleic acid RNA Ribonucleic acid Adenine Cytosine Guanine Uracil Thymine 223 Phenotype: 3D folded state and the associated catalytic activity of the molecule Genotype : primary sequence of ribonucleotides Such RNA molecules are called Ribozymes
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Ribozymes: RNA world - Dozens of ribozymes have now been characterized - All involve the formation or cleavage of bonds in RNA or DNA = the type of reaction needed to replicate nucleic acids - RNA is ubiquitous in the basic processes of cells 1. Protein synthesis (ribosomes, tRNA, mRNA) 2. Ribonucleoside triphosphates (ATP, GTP) are the energy currency of cells. 3. Deoxyribonucleotides synthesized from RNA precursors - In the lab, catalytic ability of ribozymes has been evolved using artificial selection experiments 224 The Chemical Theory (Oparin-Haldane theory) Inorganic molecules Organic molecules Biological polymers Replicating systems Protocells True cells 225 Protocells Cells provide - Compartmentalization - Concentrate organic molecules inside - Facilitates the separation of phenotype and genotype 1950’s: Sidney Fox and colleagues - Heated mixtures of a.a. and allowed them to cool - The a.a. formed protein-like polymers that formed microspheres when cooled. - Microspheres represent a model for protocells - Shows the protocells are not hard to make, in principal 226
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The Chemical Theory (Oparin-Haldane theory) Inorganic molecules Organic molecules Biological polymers Replicating systems Protocells True cells 227 The Chemical Theory (Oparin-Haldane theory) Inorganic molecules Organic molecules Biological polymers Replicating systems Protocells True cells - Proto-cells and other primitive cells may have evolved by consuming the soup of organic molecules and polymers 228 PBS: Eons What Was the Ancestor of Everything 229
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PBS: Eons Where did life come from? 230
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