In biochemistry, metabolism is the set of chemical transformations that are dedicated to maintaining life within the cells of living organisms. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures and respond to the stresses of the surrounding environment. The word “metabolism“ can also refer to all those chemical reactions that take place in living organisms, including the digestion and transport of substances within cells and between different cells, in which case the series of reactions that take place within the cells is called intermediate metabolism.