Answer:
Part of energy is stored as ATP and rest is lost as "unusable form", that is, metabolic heat.
Explanation:
According to the second law of thermodynamics, none of the energy transformation processes is 100% efficient and part of the energy is always converted into unusable form to increase the entropy of the system or surroundings. Ingestion and digestion of food into simpler elements followed by the use of these simpler nutrients for energy production stores part of energy into ATP. However, part of the energy of nutrients is converted into metabolic heat. The metabolic heat is an unusable form of energy.
