Lecture 4 - final review.docx

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Dalhousie University
Biochem & Molecular Biology
BIOC 2300
Dr.Carmichael Wallace

Lecture 4 Free energy = a property that determines whether a reaction converting reactants to products or products to reactants can occur spontaneously. Fundamental to biochemistry. - Where life forms acquire energy and how they handle and use it is central to biological chemistry. Bioenergetics - Energy = the capacity to do work or to produce heat - Thermodynamics = the study of energy transformations that accompany physical and chemical changes in matter - Bioenergetics = the branch that deals with living organisms o Work is powered with the energy provided by ATP Review of Thermodynamics - Biochemical reactions are affected by three factors: o Enthalpy total heat content o Entropy  state of disorder o Free energy energy available to do chemical work - All are state functions SO they depend only on the beginning and final states - Laws of thermodynamics o First Law: total energy is constant. Energy can be converted from one form to another but it cannot be created or destroyed o Second law: there is a tendency toward increasing disorder. The disorder is referred to as entropy - Thermodynamic transformations take place in a “universe” composed of a system and its surroundings o Energy exchange between a system and its surrounds can happen in two ways: heat or work (the displacement or movement of an object by force) First Law of Thermodynamics - Expresses the relationship between internal energy (E) in a closed system and heat (q) and work (w) - Total energy of a closed system (our universe) is constant – unlike living things which are open systems o Delta E = q + w - Enthalpy (H) is related to internal energy by the equation H = E + PV o Delta H is often equal to delta E in living systems because pressure and volume do not change appreciably o SO what does delta H tell us?  If delta H is NEGATIVE the reaction gives off heat/exothermic  If it is POSITIVE the reaction takes in heat from its surroundings/endothermic  In isothermic reactions (delta H = 0) no heat is exchanged Second Law of Thermodynamics - Physical or chemical changes resulting in a release of energy are spontaneous - Non-spontaneous reactions require constant energy input - All spontaneous processes occur in the direction that incr
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