1. 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. 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)

3. 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)

4. 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)

5. -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