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)

• 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