This chapter focuses on energy as just one aspect of body function. The chapter describes the energy-harvesting chemical reactions which happen in all human cells. For them to be possible, these cells must have access to glucose and oxygen, and must be able to dispose of the waste products, carbon dioxide and water. In a large organism such as a human, even these apparently simple requirements are challenging and are met by a complex set of physiological systems, in particular the digestive, respiratory, cardiovascular, and excretory organs of the body.
