I was doing a practice exam paper and it asked for different 'forms of free energy'. I am a physicist rather then a biologist so 'free energy' to me means Gibb's Free Energy: $$G=H-TS$$ But I cannot see how you would could have different forms of this. So is my interoperation of 'free energy' right and how can we have different forms of it?

  • $\begingroup$ Can you provide the exact context i.e. the complete question in the practice paper? $\endgroup$
    Aug 26, 2015 at 5:54
  • $\begingroup$ @WYSIWYG it was a biophysics paper and it simply said 'Give the main forms of free energy', which I guess is not very helpful, but the question came with no context apart from this. $\endgroup$ Aug 26, 2015 at 6:59
  • $\begingroup$ AFAIK, there are two types of free energy: Gibbs free energy and Helmholtz free energy (A=U-TS). However, Helmholtz free energy is almost never used in biophysics or biochemistry. Energy minimization principle in biochemistry always assumes constant temperature and pressure of the closed system. HFE is used when pressure can change. The other two thermodynamic potentials are Internal Energy and Enthalpy. Anyway, without the context it would be difficult to answer this question. $\endgroup$
    Aug 26, 2015 at 9:15


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