06. Unity and origin of life

06. Unity and origin of life - 1 What is life"An organized...

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1 What is life? “An organized genetic unit capable of metabolism, reproduction, and evolution.” (Purves, et al.) “A self-sustained chemical system capable of undergoing Darwinian evolution” (NASA definition) • Cells, metabolism, adaptation, homeostasis, growth, reproduction, evolution (Brooker, et al.) 2 What are the minimal properties of life? Metabolism: – absorption of nutrients – excretion of wastes – energy acquisition and transformation – cellular synthesis Reproduction: – Growth – duplication of all cellular components – Division of discrete units (cells) Evolution: (why do we say evolution is a characteristic of life?) – Variation, reproduction, mutation – mutation: mistakes in copying cell components 3 Where did the first life come from? • From outer space? • From nonliving substances on earth? How did all the necessary parts of a living cell come together? How can non-living matter evolve? What good is half a living cell? Organic molecules are made by living cells, so where did the first organic molecules come from? • On meteorites – organic molecules formed in interstellar clouds • Physical processes on earth: 4 – Atmospheric reactions with lightning, solar and cosmic radiation (Reducing Atmosphere Hypothesis) – Underwater reactions with volcanic vents (Deep Sea Vent Hypothesis) 5 Experimental simulations of early Earth (reducing atmosphere) conditions result in many organic compounds Spontaneous formation of simple organic molecules (monomers) under sterile, anaerobic conditions – Amino acids – Nucleotides (hypothesized) – simple carbohydrates – simple lipids Miller-Urey experiment 6 Simple organic molecules polymerized, resulting in the macromolecular structures characteristic of living cells • Phospholipids ---> Membranes • Amino acids ---> Proteins • Nucleotides ---> Nucleic acids uneven, charged topography.
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06. Unity and origin of life - 1 What is life"An organized...

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