091509-BCH311

091509-BCH311 - Lecture I: Important Points Biochemistry is...

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Unformatted text preview: Lecture I: Important Points Biochemistry is important The biochemical composition (as well as function) of all organisms is remarkably similar (biochemical unity/conservation/evolution) Macromolecules are polymers of monomers and are ubiquitous in biological systems Carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorous are the six most abundant elements in living systems The diversity and complexity of biological macromolecules can be directly attributed to the chemistry of carbon The speciFc properties of biological macromolecules are determined by their functional groups It is possible to predict whether a reaction will occur spontaneously or not by the Gibbs free energy equation: G = H - T S Gibbs Free Energy The use of thermodynamics in biology has a long history rich in confusion G = H - T S G, free energy. H, enthalpy. T, temperature in degrees Kelvin. S, entropy Enthalpy, is the heat of a reaction at constant pressure, and is related to the strength of the chemical bonds of a molecule. H is easy to measure and H values for many reactions are known Entropy, is a measure of the degree of disorder in a system. The natural tendency of the universe is in the direction of increasing dispersion of energy, and organisms employ a lot of energy into maintaining order against this tendency It takes energy to assemble, and maintain, monomers into large macromolecules, and to keep cells and their organelles and contents intact The American Heritage Dictionary gives as the rst denition of entropy, "For a closed system, the quantitative measure of the amount of thermal energy not available to do work" Entropy changes are particularly important in determining the energetics of protein folding Energy Coupling Reaction 1 is the formation of glucose 6-phosphate from glucose and inorganic phosphate - this reaction is endergonic, G is positive Reaction 2 is the hydrolysis of ATP to ADP plus inorganic phosphate - this reaction is exergonic, G negative (30.5 kJ/mol ATP) The coupling of these reactions in reaction 3 results in an overall spontaneous, exergonic process ( G 3 is negative) David S. Goodsell, Scripps Research Institute An Artists Rendition of E. coli Water: The Solvent for Biochemical Reactions Macromolecules are densely packed and ordered in an aqueous cellular environment Water is the principal component (solvent) of living cells, and plays a major role in determining the properties of macromolecules, cells and living organisms Water makes up ~70% or more of the weight of most organisms The Frst living organisms on Earth arose in an aqueous environment, and evolution has been shaped by the properties of the aqueous medium in which life began The water molecule H 2 O and its ionization products, H + and OH- , profoundly inuence the structure, self-assembly, and properties of all cellular components, including proteins, nucleic acids, and lipids Water: Physical Properties...
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091509-BCH311 - Lecture I: Important Points Biochemistry is...

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