358
9 Bioenergetics
Fig. 9.6 Equilibrium surface for extensive variables
9.13 Free Energies
9.13.1 Enthalpy
It is useful to have a quantity which characterizes processes near equilibrium
at constant pressure. The fluid in the cells of our body are at nearly constant
(atmospheric) pressure. The largest variation comes from blood pressure adding to
atmospheric, which reaches to about a 16% increase.
Consider a system variable called the enthalpy 40 defined by
H ≡ E + pV = T S +
k
μ k N k ,
(9.88)
so that for reversible processes
40 It is unfortunate that H is the symbol commonly used for E + pV . That excludes H as a symbol
for the Helmholtz free energy. Instead, A ≡ E − T S is most often used for the Helmholtz free
energy.
9 Bioenergetics
Fig. 9.6 Equilibrium surface for extensive variables
9.13 Free Energies
9.13.1 Enthalpy
It is useful to have a quantity which characterizes processes near equilibrium
at constant pressure. The fluid in the cells of our body are at nearly constant
(atmospheric) pressure. The largest variation comes from blood pressure adding to
atmospheric, which reaches to about a 16% increase.
Consider a system variable called the enthalpy 40 defined by
H ≡ E + pV = T S +
k
μ k N k ,
(9.88)
so that for reversible processes
40 It is unfortunate that H is the symbol commonly used for E + pV . That excludes H as a symbol
for the Helmholtz free energy. Instead, A ≡ E − T S is most often used for the Helmholtz free
energy.