Several forms of potential energy are biologically significant, the strength and the efficiency of the potential energy are strongly connected to entropy, therefore, it can become stronger or weaker based on circumstances affiliated with the form, consequently, it will have an impact on the metabolic processes and immune system (14).
The most important form which is central to all biological process is the potential energy stored in bonds that connecting atoms in the form of molecules (15). In the catabolic reaction, large molecules such as proteins, lipids, carbohydrates (from food), are either broken or hydrolyzed into smaller molecules, this reaction is spontaneous, and proceed from a large molecule with high potential to a small molecule with low potential. As a result, the number of molecules increases and their size decreases, thereby increasing entropy (16). A healthy body regulates these molecules either by excretion or by utilization as macromolecule building blocks. The catabolic process is an important metabolic process and used to produce energy, the reaction is spontaneous with regards to energy demand and entropy-driven.
A second biologically important form of potential energy is stored in a highly concentrated area. Due to the constant movements of ions and molecules, in the body, substances move from a high concentration area with high potential to low concentration with high entropy. The passive diffusion of substances through membranes produce a solution with more random movement. This movement is entropy-driven, the result is a concentration gradient and diffusion will continue until this gradient has been eliminated. All cells form concentration gradients between their interior and the external fluids by selectively exchanging nutrients, waste products, and ions with their surroundings.
A third form of potential energy in cells is an electric potential, the energy of charge separation in cells. The electrical polarity, with −70 mV resting potential, exists almost in all cells of the body with the exception of nerve and muscle cells. In neurons, action potentials play a central role in cell-to-cell communication. Certain neurotransmitters act as an exciter and promote the generation of large depolarizations by ~15–20 mV above the resting value of −70 mV to a threshold of about ~−55 mV. At this threshold potential, the cell membrane opens up allowing Na+ transport, with complete depolarization, an action potential is generated. Other neurotransmitters act as an inhibitor and prevent the propagation of action potential (17).