6 Metabolism and body temperature
Metabolism is the technical name given to the sum of all the chemical transformations inside cells. Many such changes involve building up complex chemicals from simpler building blocks – for example, the proteins and fats for lactation that were described earlier. In animals, the energy that such ‘building-up’ processes require comes from the process of breaking down foodstuffs – the progressive breaking down in our bodies of the complex macromolecules that comprise our diet. The chemical reactions that take place in an animal are affected by temperature. The adaptations that enable a mammal to regulate body temperature form a key mammalian feature – the ability to maintain body temperature using internal body heat.