It is an immutable constant. In living system the work done at constant T and P is less than the theoretical estimate. ATP has 3 to 4 closely spaced negative charges, which repel each other. Some of the tension is relieved when the terminal phosphate is cleaved off. The electrons are in a configuration with less energy in the hydrolysis products.
Cells contain transducers which convert energy from electron flow to chemical energy.
F. Reducing equivalent is a single electron equivalent participating in a redox reaction, whether it is electron, H atom, hydride ion , or direct reaction with oxygen D. Biological redox usually undergo enzymatic dehydrogenation to lose 2 reducing equivalents at a time, and because each O-atom can accept 2 reducing equivalents, in biological oxidations we think of a pair of reducing equivalents passing from substrate to oxygen. Standard redox potentials of conjugate redox pairs are shown in Table 13.7. B. Free energy changes accompany electron transfers 1. Electrons tend to move in such a direction that the free energy of the system is aways decreasing. The greater the difference in the standard potentials between two redox pairs the greater the free energy loss as e-'s pass from electron negative to electron positive.