Abstract Because of essential dependence of medical sciences on basic sciences, eventual misconceptions in basic sciences may exert a profound detrimental effect on medical sciences. One such example relates to a concept taken from chemistry that the reducing agent represents the substantial energy source in the process of oxido-reduction. While the recognition of the substantial source of energy is of little importance in technique, it is of utmost importance in medicine for assessment of results of interactions in vivo of various energetic forms and particularly for appreciation of consequences of energy exchange on dynamics of organismal structure. Three proofs are given here that the oxidizing agent, not the reducing agent, is the source of energy in chemical and biochemical oxido-reductive processes. On the other hand, energy content of organic substances being major organismal constituents is represented mostly by energy stored in chemical bonds between their monomeric units. Circumstantial evidence indicates that energy content of one chemical bond between monomeric units per a weight unit is lower in lipids than in proteins or carbohydrates. Regarding structural disorders, there are principally two opposite, mutually exclusive phenomenons: degeneration resulting from loss of energy on one side, and hypergeneration enabled by excess of energy on the other. Disorders of stress and obesity represent states with relative lack of energy. While stress implies a degenerative process usually resulting from acute loss of energy, obesity represents a chronic disturbance of proportions of constitutive substances of the body in favour of less energy-rich substances and therefore might be regarded as a kind of degeneration. The phenomenon of hypergeneration, being contrary to degeneration usually appears as a local overformation of structure called neoplasia.