Describe the respiratory balance sheet.

Explanation

It is possible to make calculation of the net gain of ATP for every glucose molecule oxidised but in reality this can remain only a theoretical exericse. These calculations can be made only on certain assumptions that :
(1) There is a sequential orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle and ETS pathway following one after another.
The NADH synthesised in glycolysis is trnasferred into the mitochondria and undergoes oxidative phosphorylation.
(3) None of the intermediates in the pathway are utilised to synthesize any other compound.
(4) Only glucose is being respired-no other alternative substrates are entering in the pathway at any of the intermediary stages.
But this kind of assumptions are not really valid in a living system .
All pathways work simultaneously and do not take place one after another.
Substrates enter the pathways an are withdrawn from it as and when necessary.
ATP is utilised as and when needed .
Enzymatic rates are controlled by multiple means. Yet it is useful to do this exercise to appreciate the beauty and efficiency of the living system in extraction and storing energy.
Hence, there can be a net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose.