UT Knoxville BIOL 140 - Chapter 3 (67 pages)

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Chapter 3



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Chapter 3

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Pages:
67
School:
University of Tennessee
Course:
Biol 140 - Organization/Function of Cell
Organization/Function of Cell Documents

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CHAPTER 3 2011 Pearson Education Inc Revisiting the Theory of Chemical Evolution Oparin Haldane 1923 1929 Modern life arose through a series of endergonic chemical reactions 1 Production of small organic compounds i e formaldehyde H2CO hydrogen cyanide HCN 2 Formation of mid sized molecules from these small compounds i e amino acids simple sugars These molecules combined with ocean water to form prebiotic soup Mid sized building blocks combine to form large molecules i e proteins complex carbohydrates 4 Life became possible when one of these large molecules selfreplicated 2011 Pearson Education Inc Early Origin of Life Experiments Could the first steps of chemical evolution have occurred on ancient Earth To find out Stanley Miller 1953 combined methane CH4 ammonia NH3 and hydrogen H2 in a closed system with water and applied heat and electricity as an energy source The products included hydrogen cyanide HCN and formaldehyde H2CO important precursors for more complex organic molecules and amino acids In more recent experiments amino acids and other organic molecules have been found to form easily under these conditions 2011 Pearson Education Inc The Structure of Amino Acids All proteins are made from just 20 amino acid building blocks All amino acids have a central carbon atom that bonds to NH2 COOH H and a variable side chain R group In water pH 7 the amino base and carboxyl acid groups ionize to NH3 and COO respectively this helps amino acids stay in solution and makes them more reactive 2011 Pearson Education Inc 2011 Pearson Education Inc The Nature of Side Chains The 20 amino acids differ only in the unique R group attached to the central carbon The properties of amino acids vary because their R groups vary 2011 Pearson Education Inc Functional Groups Affect Reactivity R groups differ in their size shape reactivity and interactions with water 1 Nonpolar R groups hydrophobic do not form hydrogen bonds coalesce in water 2 Polar R groups hydrophilic form hydrogen



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