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Lecture 11

BSC 196 Lecture 11: lecture 11

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Biological Sciences
BSC 196

Chemical and physical processes on early Earth may have produced simple cells through 4 stages Abiotic synthesis of small organic molecules amino acids, nitrogenous bases Joining of these small molecules into macromolecules proteins, nucleic acids Packaging of molecules into protocells membrane-bound droplets with different internal chemistry Origin of self-replicating molecules made inheritance possible In the 1920s, A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing (electron adding) environment water vapor plus compounds from volcanic eruptions (nitrogen, CO2, methane, ammonia, hydrogen) organic molecules could have formed from simple molecules energy promoting this synthesis? lighting or UV radiation In 1953, Miller and Urey conducted lab experiments showing that synthesis of organic molecules in a reducing atmosphere is possible apparatus: vapor from boiling water circulated through an atmosphere of methane, ammonia, and hydrogen this mixture passed by electric spark cooled so that vapor condensed to form a pool in ~ week, solution contained a number of amino acids small organic molecules alone (amino acids, nitrogenous bases) not sufficient for life cells posses many kinds of macromolecules: proteins and nucleic acids RNA monomers (nucleotides) have been produced spontaneously from simple molecules Small organic molecules polymerize (i.e., form macromolecules like nucleic acids) when they are concentrated on hot sand, clay, or rock life forms must carry out reproduction and energy processing (metabolism) first protocells: vesicles (fluid-filled bubbles surrounded by membrane) form spontaneously when lipids or other organic molecules added to water reflect two key properties of life: replication and metabolism maintain an internal chemical environment capable of reproduction addition of clay (common on early earth) increases the rate at which vesicles are produced paradox of life cell needs enzymes to carry out cellular functions (normally proteins) but proteins unable to replicate cell needs to be able to replicate (normally via DNA) but DNA cannot carry out cellular functions seems unlikely that DNA and proteins appeared simultaneou
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