Metabolism is such a big word to explain a simple idea. We all need energy to survive. Whether we are plants, animals, or bacteria, we all need energy. Energy doesn't just float around in a form we can use to survive. We need to eat (mainly sugars) and digest food. That process of chemical digestion and its related reactions is called metabolism. Metabolism is the total of all the chemical reactions an organism needs to survive. Sounds a lot like biology. Why is it here in biochemistry? There are two main chemical processes that make our world go round, involving two simple chemical reactions. The first is called glycolysis. That's the breakdown of sugars. The second process is called photosynthesis. That is the series of reactions that builds sugars. You need to remember that the overall metabolism of an organism includes thousands of chemical reactions. The reactions in glycolysis and photosynthesis are just the cornerstones to life.