BIOL 1202 Chapter : Biology1202Chapter25
Document Summary
Conditions on early earth: atmosphere, co2; ch4; nh3; h2s; h2o, no free oxygen, abundant energy to drive reactions, frequent storms with much lightening, frequent volcanic eruptions, frequent meteor impacts, uv light from the sun, because no ozone layer. Testable hypotheses explaining the origin of life: abiotic synthesis of small organic molecules, joining these molecules into polymers, packaging these molecules into protobionts , the origin of self-replicating molecules. Alternate hypotheses: first organic compounds may have been synthesized near hydrothermal vents, extraterrestrial origin. Abiotic synthesis of polymers: small organic molecules polymerize when they are concentrated on hot sand or clay. Protobionts: aggregates of abiotically produced molecules surrounded by a membrane, liposomes can form when lipids or other organic molecules are added to water, figure 25. 3. The chicken or the egg: now, dna rna protein, need proteins to synthesize more dna, then, earliest cells used rna to store information, ribozymes to catalyze reactions. Possible sequence leading to first prokaryotes: purple figure.
