• Free Energy: portion of systems energy that can perform work when temperature and pressure are uniform throughout (not heat)
  • Formula ΔG= ΔH-TΔH
    • ΔG= Free energy change
    • ΔH = Enthalpy, change in total energy/heat content
    • ΔS = Entropy, what’s lost as heat
  • Spontaneous processes occur without energy input, – ΔG (quickly or slowly)
    • Increases entropy, decrease H, and releases energy for work
  • Nonspontaneous: requires energy, decreases entropy, + ΔG
    • monomer to polymer

Free Energy, Stability, and Equilibrium

  • ΔG(result energy) = G (final) – G (initial) ← net energy
  • ΔG = system loses free energy and becomes more stable
  • More energy/more unstable → lower ΔG/more stable/less work capacity


Equilibrium is a state of maximum stability (low energy); forward and reverse actions occur at the same rate so there is no net change→ no net production of reactants or products

  • A process is spontaneous and can perform work only if it is moving towards equilibrium
  • System at equilibrium = lowest  ΔG
  • Ex: Chemical reactions where neither reactant or product are used
  • A cell at metabolic equilibrium is dead cuz systems can do no work
    • So cells constantly have materials in/out which stops from reaching equilibrium
      • cellular respiration: the product does not accumulate, instead becomes the reactant in next step
    • Reaction at equilibrium will stay that way even if the enzyme is added!