Abstract
The survival and reproduction of human life requires calcium, not only outside the cell for maintenance of skeletal and tissue architecture, and for key extracellular enzymes such as those involved in blood clotting or digestion, but also inside cells controlling their behaviour (Campbell 1983). The evolutionary success of eukaryotic cells has been critically dependent on the development of mechanisms which enable the whole organism to regulate its behaviour in response to both internal and external stimuli. Signals from the brain can provoke release of neurotransmitters from nerve terminals leading to muscle movement. Individual cell movement occurs in neutrophils, the first cells to appear at a site of infection. The daily fasting-feeding cycle requires regulation of intermediary metabolism by substrates and hormones, in order to channel nutrients through the pathways of lipid or carbohydrate oxidation necessary for supplying the energy needs of individual tissues and the body as a whole (Campbell and Hales 1976).
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