2-ch13 Introduction to Metabolism PDF

2 -ch13 Introduction to Metabolism Learning Objectives Autotrophs, Heterotrophs Catabolism, anabolism Thermodynamics : the first law, the second law 13.1 Bioenergetics and thermodynamics Universe, system, & surroundings Gibbs free energy, Enthalpy, & Entropy standard free-energy chan...

2 -ch13 Introduction to Metabolism Learning Objectives Autotrophs, Heterotrophs Catabolism, anabolism Thermodynamics : the first law, the second law 13.1 Bioenergetics and thermodynamics Universe, system, & surroundings Gibbs free energy, Enthalpy, & Entropy standard free-energy change, ∆G′° and standard equilibrium constant, K′eq 13.2 Chemical Logic and Common Biochemical reactions Neutrophiles and electrophiles Carbonyl groups Kinase, phosphorylase, phosphatase Catabolic Pathways Converge. Anabolic Pathways Diverge. 13.1 Bioenergetics and Thermodynamics Bioenergetics Is the Quantitative Study of Energy Transductions energy transductions = changes of one form of energy into another Biological Energy Transformations Obey the Laws of Thermodynamics the first law of thermodynamics is the principle of the conservation of energy the second law of thermodynamics says that the universe always tends toward increasing disorder  Question Which statement describes the second law of thermodynamics? A. In all natural processes, the entropy of the universe increases. B. The entropy of a system at absolute zero is a well-defined constant. C. For any physical or chemical change, the total amount of energy in the universe remains constant. D. Energy may be created or destroyed, but it cannot change form or be transported from one region to another.  Systems and Their Surroundings reacting system = the collection of matter that is undergoing a particular chemical or physical process – can be closed or open universe = the reacting system and its surroundings together living cells and organisms are open systems, exchanging material and energy with their surroundings  Enthalpy, H enthalpy, H = the heat content of the reacting system – reflects the number and kinds of chemical bonds (covalent and noncovalent) in the reactants and products – when ∆H is negative, the reaction releases heat and the reaction is exothermic – when ∆H is positive, the reaction takes up heat and the reaction is endothermic  Entropy, S entropy, S = a quantitative expression for the randomness or disorder in a system – when ∆S is negative, the reactants are less complex and more disordered than the products – when ∆S is positive, the products are less complex and more disordered than the reactants  Free Energy, G free energy, G = expresses the amount of energy capable of doing work during a reaction at constant temperature and pressure – when ∆G is negative, free energy is released and the reaction is exergonic – when ∆G is positive, free energy is gained and the reaction is endergonic  Free Energy Change, ∆G free-energy change, ∆G = ∆H − T∆S (13-1) – ∆H is negative for a reaction that releases heat – ∆S is positive for a reaction that increases the system’s randomness spontaneous reactions occur when ∆G is negative  Discussion/Question Which thermodynamic quantity relates MOST to breaking the α(14) O-glycosidic linkages between the two glucose molecules in maltose ? (assuming that there was no heat produced/absorbed during the reaction) A. enthalpy B. entropy C. Gibbs free energy D. Equilibrium E. Keq