Typically, it is in the form of heat which is dissipated from living organisms. For example, kinetic energy enables particles to move via diffusion . Potential energy is energy possessed by something by virtue of its position or condition. There are two basic types of energy relationships between organisms and their environments, autotrophy and heterotrophy . However, the ultimate source of biologically useful energy is sunlight, which is incorporated into chemical bonds of organic molecules during photosynthesis.
Reactions involve transfer of electrons .
Since electrons are subatomic elemental units of energy, every phenomenon resulting in movement of electrons to or from substances involves energy. A loss of free energy results from oxidation. Simultaneously, another substance exhibits reduction and gains one or more electrons and free energy. During all chemical reactions, energy transformations occur. The terms exergonic and endergonic are used to denote release or uptake, respectively, of free energy by reactants.