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Energy and Chemical Reactions

5 Pages

Course Code
BIOL 1117
Christopher Richardson

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L5-The Chemistry of Life 9/12/13 • Work and Energy o Energy: capacity to do work  Work is the amount of energy transferred by a force, which acts over a distance in the same direction as that force  Work is the action of moving something whether it is a muscle or a molecule o Potential energy: energy contained in an object because of its position or internal state  chemical energy: potential energy stored in the bonds of molecules  free energy: potential energy available in a system to do work • The most relevant free energy in a physiological system is stored in chemical bonds • Energy o Kinetic energy: energy of motion; energy that is doing work  heat: a form of kinetic energy, which is the total kinetic energy of molecular motion • Heat is not directly available to do work  electromagnetic energy: the kinetic energy of moving ‘packets’of radiation called photons o Ions in greater concentration on one side of a membrane than the other have potential energy o Ions flowing through to the other side of the membrane have kinetic energy, which can be used to power reactions o Electrical energy is potential energy when charged particles are stored up in a battery at terminal or one side of a membrane o Electrical energy is kinetic energy when the motion of those particles produces an electric current o Work done on an object or a particle is equal to the change in kinetic energy of an object or a particle • Chemical Reaction o Chemical reaction: a process in which a covalent or ionic bond is formed or broken o Chemical equation: symbolizes the course of a chemical reaction  reactants (on left) ® products (on right)  Chemical bonds are broken in reactants and formed in products as part of the reaction o Classes of Chemical Reactions  Decomposition reactions • Large molecule breaks down into two or more smaller ones • AB ®A+ B  Synthesis reactions • Two or more small molecules combine to form a larger one • A+ B ®AB  Exchange reactions • Two molecules exchange atoms or group of atoms • AB + CD ® ABCD ® AC + BD • Reversible Reactions o Can move in either direction under different circumstances o symbolized with double-headed arrow o CO + 2 O <2> H CO <2> H3O + H 3- +  In respiratory, urinary, and digestive physiology o Work until equilibrium is reached o Law of mass action determines direction  Proceeds from the side of equation with greater quantity of reactants or products to the side with the lesser quantity of either  Thus reactants and product concentrations affect the direction of net reaction  This means if you either add product or move reactants, this will drive the reaction in reverse (shift to the left)  Or if you remove product or add reactants, this will drive the reaction forwards (shift to the right) • Reversible/Irreversible Reactions o Reversible reactions eventually exist in a state of equilibrium with ratio of products to reactants is stable o Irreversible reactions occur when almost all reactants have become product and most of the energy has been released • Chemical Reactions o Basis for chemical reactions is molecular motion and collisions. o In general, a successful chemical reaction occurs when molecules collide at the correct orientations and with enough force or sufficient energy o Energy of activation (E ) iA the minimum amount of energy required for a successful reaction to occur. This energy must come from the collision. o Reaction rates increase when energy of activation decreases. o The
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