General Chemistry Principles, Patterns, and Applications, 2011

The high-energy phosphoric acid anhydride bond in ATP stores energy released during the
oxidation of nutrients. Hydrolysis of the high-energy bond in ATP releases energy, forming
adenosine diphosphate (ADP) and phosphate.
Under standard conditions in biochemical reactions, all reactants are present in aqueous concentrations
of 1 M at a pressure of 1 atm. For H + , this corresponds to a pH of zero, but very little biochemistry occurs
at pH = 0. For biochemical reactions, chemists have therefore defined a new standard state in which the
H + concentration is 1 × 10 − 7
M (pH 7.0), and all other reactants and products are present in their usual
standard-state conditions (1 M or 1 atm). The free-energy change and corresponding equilibrium constant
for a reaction under these new standard conditions are denoted by the addition of a prime sign (′) to the
conventional symbol: ΔG°′ and K′. If protons do not participate in a biological reaction, then ΔG°′ = ΔG°.
Otherwise, the relationship between ΔG°′ and ΔG° is as follows:
Equation 18.54
ΔG°′ = ΔG° + RT ln(10 −7 )n
where ΔG°′ and ΔG° are in kilojoules per mole and n is the number of protons produced in the reaction. At
298 K, this simplifies to
Equation 18.55
ΔG°′ = ΔG° − 39.96n
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