It would seem that the contributor is trying to understand cell biochemistry by taking a rather static and sterile, text book approach to the subject. In the real system the levels of constituents are not rigidly fixed as classical biochemistry would suggest. This is partly because the subsystems are not isolated but interact and largely because all living entities, not least cells, are highly autodynamic because the relevant control reactions operate in their oscillatory mode. Thus ATP levels, NAD coenzyme oxidation state and other components (including protein levels, enzyme activities and even cell shape) are varying rhythmically at high frequency. (see for example, Cell Biol. Intl. 24: 569-580, 2000). Unfortunately most cell scientists ignore this reality with the consequence that many of their experimental results are open to question and they are unable to provide answers for major problems.