free energy

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energy

 [en´er-je]
power that may be translated into motion, overcoming resistance or causing a physical change; the ability to do work. Energy assumes several forms; it may be thermal (in the form of heat), electrical, mechanical, chemical, radiant, or kinetic. In doing work, the energy is changed from one form to one or more other form(s). In these changes some of the energy is “lost” in the sense that it cannot be recaptured and used again. Usually there is loss in the form of heat, which escapes or is dissipated unused; all energy changes give off a certain amount of heat.ƒ

All activities of the body require energy, and all needs are met by the consumption of food containing energy in chemical form. The human diet comprises three main sources of energy: carbohydrates, proteins, and fats. Of these three, carbohydrates most readily provide the kind of energy needed to activate muscles. Proteins work to build and restore body tissues. The body transforms chemical energy derived from food by the process of metabolism, an activity that takes place in the individual cell. Molecules of the food substances providing energy pass through the cell wall. Inside the cell, chemical reactions occur that produce the new forms of energy and yield by-products such as water and waste materials; see also adenosine triphosphate.
free energy (Gibbs free energy (G)) the energy equal to the maximum amount of work that can be obtained from a process occurring under conditions of fixed temperature and pressure.
nuclear energy energy that can be liberated by changes in the nucleus of an atom (as by fission of a heavy nucleus or by fusion of light nuclei into heavier ones with accompanying loss of mass).

free en·er·gy (F),

a thermodynamic function symbolized as F, or G (Gibbs free energy), = H - TS, where H is the enthalpy of a system, T the absolute temperature, and S the entropy; chemical reactions proceed spontaneously in the direction that involves a net decrease in the free energy of the system (that is, ΔG < 0).

free en·er·gy

(F) (frē en'ĕr-jē)
A thermodynamic function symbolized as F, or G (Gibbs free energy), =H-TS, where H is the enthalpy of a system, T the absolute temperature, and S the entropy; chemical reactions proceed spontaneously in the direction that involves a net decrease in the free energy of the system (i.e., ΔG < 0).

free energy

the amount of energy that is available for work when released in a chemical reaction. For example, when a molecule of ATP is hydrolysed to ADP + P, the free energy released is about 34 kJ.