Transcript Thermodynamics / Free Energy & ATP

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