Basics of Metabolism
Metabolism is a process of energy acquisition and conversion. It is necessary because organisms are constantly undergoing cellular changes--they are not in a state of equilibrium. Metabolism is an attempt to regulate cellular conditions by making internal changes to maintain a steady cellular state. As a general rule, nature's tendency is towards conditions of disorder. This means that disorderly conditions are energetically favorable--they release energy. Highly ordered and organized conditions are not energetically favorable and require energy to occur. As a result, the thousands of reactions that constantly occur inside us to maintain cellular organization need energy. The body produces this needed energy by breaking down ATP, and then using this energy to promote energetically unfavorable, but biologically necessary reactions. http://www.sparknotes.com/biology/cellrespiration/intro/section2.rhtml
Adenisine Triphosphate (ATP) - The molecule from which cells derive energy. Comprised of an adenisine molecule bonded to three phosphates. Each phosphate bond contains energy, especially the third bond. By breaking that one bond and reducing ATP to adenisine diphosphate (ADP), the cell can get the energy to carry out its various processes. http://www.sparknotes.com/biology/cellrespiration/intro/section2.rhtml
In order to begin any of these processes, ...
This solution assists in explaining how humans gain our metabolic energy (ATP) from the sun. References are provided.