Metabolism: An Introduction Totality of an organism’s processes Molecular interactions make this an emergent property Concerned with managing cellular material and energy Anabolic Pathways Catabolic Pathways These Anabolic/Catabolic reactions can be coupled so that energy released from a catabolic rx can drive an anabolic rx.

Catabolic Pathways RELEASE ENERGY by breaking down complex molecules to simpler ones

ANABOLIC PATHWAYS CONSUME ENERGY to build complicated molecules from simpler ones

Organisms Transform Energy Energy: Capacity to do work Kinetic Energy: Energy in the process of doing work (energy of motion) ex.:Light,Thermal. Potential Energy: Energy of position (energy due to arrangement or location). Ex.:Rock on hill, chemical energy ENERGY CAN BE TRANSFORMED FROM ONE FORM TO ANOTHER. Ex: Gas-motion

Energy Transformations and Thermodynamics Thermodynamics: The study of energy transformations First Law of Thermodynamics: Energy can’t be created or destroyed, only transferred or transformed Second Law of Thermodynamics: Every energy transfer increases ENTROPY Entropy: Quantitative measure of disorder (proportional to randomness)

More Thermodynamics Vocab. Closed System: Collection of matter being studied which is isolated from the surroundings Open System: A system in which energy can be transferred from the system and its surroundings

ENTROPY The entropy of a system may DECREASE, but the entropy of the system plus its surroundings must always INCREASE. Animals: Maintain highly ordered structure at the expense of their surroundings Take in complex high energy molecules as food and extract energy in order to create and maintain order Return simple low energy molecules and heat to surroundings

Gibbs-Heimholtz equation: FREE ENERGY The amount of energy that is available to do work Free Energy:G Total Energy or Enthalpy: H Temperature in Kelvin Degrees: T Entropy: S Free energy is the difference between the total energy and the energy NOT available to do work. Gibbs-Heimholtz equation: G S H- T =

Significance of Free Energy Indicates a maximum amount of a system’s energy which is available to do work Indicates whether a reaction will occur spontaneously or not A spontaneous reaction is one that will occur without any additional energy The change in Free energy of a system DECREASES in a spontaneous reaction. A decrease in enthalpy (or total energy) or a n increase in entropy reduce the free energy, and make a spontaneous more likely Increased Temperature favors spontaneity These reactions tend toward a more stable state

Free Energy and Equilibrium There is a relationship between chemical equilibrium and free energy change As the reaction approaches equilibrium, the free energy decreases As a reaction is pushed away from equilibrium, free energy increases. AT equilibrium, there is no net change in the system (0 change in free energy)

Free Energy and Metabolism EXERGONIC REACTIONS: A reaction with a net LOSS of free energy Spontaneous The change in Free energy (downhill) is the max. amount of work the Rx can do Products have less free energy than rectants ENDERGONIC REACTIONS: An energy requiring reaction that occurs with a net GAIN of free energy Absorbs energy Products store more free energy Non-spontaneous The change in free energy (uphill) is the min. amount of energy required to drive the rx

What the………..(O.K., here’s some examples) Burning (oxidation) of one mole of glucose: EXERGONIC and releases 686 Kcal/mol. Actually Free energy is said to be NEGATIVE or-686Kcal/mol. Production of 1 mole of glucose is ENDERGONIC and requires the energy input of +686Kcal/mole

Energy Units Joule(J): .239 calorie Kilojoule(kJ): 1000J or .239 Kcal Calorie(cal): 4.184J

METABOLIC DISEQUILIBRIUM At equilibrium the system can’t do work: Change of free energy is 0. Necessity of life: A cell at total equilibrium is dead These reversible reactions are pulled one way or the other because the products of 1 become the reactants for another