Thermodynamics / Free Energy & ATP Metabolic pathways create and use energy to manage the material resources of the cell. The study metabolism is bioenergetics (the study of how organisms manage their energy resources). There are 2 major pathways: Catabolic - releases energy as molecules are broken down Anabolic - consumes energy as molecules are built up Reactions are coupled in biological organisms but never in equilibrium Anabolic Catabolic

2 Laws of Thermodynamics the 2 laws of thermodynamics and can be related to the free energy (DG) of a system. 1st Law - Energy cannot be created nor destroyed.....only changed or transferred. 2nd Law - All energy processes lead to entropy (disorder and the release of heat)

Basic Forms of Energy Kinetic - Energy of motion Thermal - Heat produced by the random motion of atoms within a substance Light - EMR created by 2 perpendicular waves Potential - Energy of position or the ability to produce kinetic energy Gravitational - anything above the ground Chemical - energy stored in the bonds of molecules (fats 9Kcal/g, carbs 4Kcal/g, & protein 4Kcal/g)

Gibbs Gibbs described that the energy of any system could be put into an equation that described the transfer of heat while following the 2 laws of thermodynamics. DG = DH - TDS or DGFinal - DGInitial G = Free energy H = Enthalpy (energy in a biological system - Neg = exothermy & Pos = edothermy) T = Temperature in Kelvin (C + 273) S = Entropy of the system Spontaneous reactions MUST have a -DG where the products are more stable than the reactants. In order for that to occur the following must be true: DH is decreasing (a release of enthalpy from a biological system) T is increasing (energy lost to heat) DS is increasing (products are less ordered than the reactants)

-DG is exergonic (releasing energy) We relate the free energy (DG) to metabolic systems in the following ways. -DG is exergonic (releasing energy) C6H12O6 + 6O2 g 6CO2 + 6H2O DG = -686 kcal/mol DG = energy lost to the environment in the process DG is endergonic (storing energy) 6CO2 + 6H2O g C6H12O6 + 6O2 DG = 686 kcal/mol DG = energy gained from the environment in the process Metabolic process NEVER reach equilibrium in the cell