 The ox-phos controversy was about the mechanism by which respiration (i.e., the oxidation of energy-rich compounds) is coupled to the phosphorylation of ADP (adenosine diphosphate) to ATP (adenosine triphosphate). The reverse reaction, hydrolysis of ATP to ADP and inorganic phosphate, is used by cells to power numerous biochemical reactions such as the synthesis of proteins as well as small molecules, the replication of DNA, locomotion, and many more (the energy for muscle contraction is also provided by ATP hydrolysis). Thus, ATP functions like a universal biochemical battery that is used to power all kinds of cellular processes. So how can the cell use the chemical energy contained in food to charge these batteries? A first pathway that generates ATP from ADP to be described was glycolysis, the degradation of sugar. This pathway does not require oxygen. The way it works is that the breakdown of sugar is used by the cell to make an activated phosphate compound – a so-called high-energy intermediate – that subsequently transfers its phosphate group to ADP to make ATP. 