Final answer:
The change in free energy from the complete oxidation of 1 NADH molecule leads to the production of 3 ATP molecules with an energy efficiency of 42%, while the remaining 58% of the energy contributes to heating the body.
Step-by-step explanation:
To calculate the change in free energy from the complete oxidation of 1 NADH molecule, we consider that the oxidation of NADH in the electron transport chain is associated with the production of ATP.
The potential difference between the redox pairs (NADH/NAD+ and O2/H2O) is 1.14 volts, which is equivalent to an energy change of -218 kJ/mol. Given that each ATP synthesis requires 30.5 kJ/mol, the production of 3 ATP molecules from the oxidation of 1 NADH corresponds to an energy requirement of 91.5 kJ/mol.
Thus, the energy efficiency of this reaction is (91.5 kJ / 218 kJ) x 100%, which is approximately 42%. The remainder of the energy, 58%, contributes to body heat.