Utilization of energy is one of the more important characteristics of life. Our bodies accumulate useful energy and constantly build structures with increasing complexity and lower and lower entropy.
This seems like the total opposite of what takes place in the inanimate world in which all processes universally lead to lower useful energy levels and higher levels of disorder (entropy).
Yet, in the complex process we call "life", the very opposite takes place. How?
A good place to start an investigation of biological energy begins with a plant, a 15-foot tall perennial grass that grows in Louisiana, Florida, Texas and Hawaii, where it is harvested commercially for the contents of its stems.
Scientifically the plant is known as Saccharum officianarum, but most people know it as sugar cane.
Within the stems of this grass, humans have found the world's most popular sweetener, the sugar called sucrose. Sucrose is made up of one molecule of fructose linked to one molecule of glucose to form a di-saccharide (di - meaning two and saccharide meaning sugar).
Saccharum officianarum makes and stores sucrose molecules, and humans harvest and use this sugar as a major source of food. Millions and millions of tons a year enter our diet in everything from tomato ketchup to bread.
The story of sucrose is the story of biological energy. There are many forms and many ways in which biological energy is used by animals and plants. All can be seen by following the life of a molecule of this disaccharide.