Bio lecture 1 - Lecture 1: The Earth formed 4.6 Billion...

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Lecture 1: The Earth formed 4.6 Billion years ago. Atmosphere may have contained CO2, water vapor, CO, H2, N2, some ammonia (NH3), hydrogen sulfide (H2S, and methane, although ultraviolet radiation from the sun most likely broke these reduced molecules down rapidly. The early atmosphere probably contained little or no free oxygen (O2). Earths atmosphere was probably strongly reduced, which means that any free oxygen would have reacted with other elements to form oxides, thus oxygen would have been tied up in compounds. If it was no already occupied, it would have oxidized the organic molecules that are necessary building blocks in the origin of life, because oxygen is very reactive. Prebiotic Soup hypothesis: states the organic molecules that are the building materials for organisms, formed near earth’s surface. Oparin and Haldane proposed that simple organic molecules such as sugars, nucleotide bases, and amino acids could form spontaneously from simple raw materials. Their hypothesis was tested by Miller and Urey who designed a closed apparatus that simulated conditions that presumably existed on early earth. Their atmosphere contained H2, CH4, H20 and NH3 which they exposed to electric charge (simulating lightning). The experiment confirmed that amino acids and other organic molecules had formed. Scientists have synthesized several different protobionts, which are assemblages of abiotically synthesized (not produced by organisms) organic polymers, which have been recovered prtobionts that resemble living cells in many ways. This may explain how life started on earth and how nonliving molecules took the big step toward becoming living cells. RNA World is a model that states that the chemistry of prebiotic Earth gave rise to self-replicating RNA molecules that functioned as both enzymes and substrates for their own replication (RNA creating RNA). Ribozymes are enzymatic RNA which have catalytic properties. Ribozymes may have catalyzed their own
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Bio lecture 1 - Lecture 1: The Earth formed 4.6 Billion...

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