Defining Metabolism
Metabolism can be defined as the process by which living tissues or cells take up and convert the nutritive material into energy. The final product in this process is a molecule called adenosine triphosphate (ATP). Cells use ATP as an energy unit to perform their specialized functions. Metabolism, then, is the final step in the three-stage process we are learning about.
The individual cells receive the nutrients--primarily vitamins, minerals (and other micronutrients not covered in this course)--from the blood, and are ingested through the cell wall and make use of them to produce ATP via cellular metabolism. From there, the incoming nutrients are converted into energy. The energy can be used for various physiological functions including muscle contraction, neuron firing, oxygen intake, and many other specialized functions within the body. Metabolism occurs within the cells and requires this basic energy unit, ATP.