Release of Energy from Foods, and the Concept of ―Free Energy‖ Most of the chemical reactions in the cells are aimed at making the energy in foods available to
the various physiologic systems of the cell. For instance, energy is required for muscle activity,
secretion by the glands, maintenance of membrane potentials by the nerve and muscle fibers, synthesis
of substances in the cells, absorption of foods from the gastrointestinal tract, and many other functions.
Coupled Reactions.
All the energy foods—carbohydrates, fats, and proteins—can be oxidized in the
cells, and during this process, large amounts of energy are released.
