Expert: Walter Hintz - 2/18/2008

Question
Dear Sir, Please clear my confusion�c�c..

We have studied in Respiration, that when one molecule of Glucose is oxidized it produces 36 or 38 ATP, and when one ATP is hydrolyze it produce 7 Kcal of energy i.e.

Glucose + H2O �¨ CO2+ H2O +38 ATP
ATP + H2O �¨ ADP + iP + 7 Kcal

But Sir, I have seen in many books that when one gram of glucose is oxidize in a body it produce 7.1 kcal of energy. So did one gram of glucose contain less than one molecule of glucose?
If one gram of glucose contain more than one molecule of glucose than one gram should produce more than 266 Kcal of energy�c  

Answer
I am not sure of the figures here.  I do know that 1 g of carbohydrate produces 3.75 kcal not 7.1 kcal
You may be confusing the energy in a glucose molecule and the energy stored in a phosphate bond in ATP.  In energy units a phosphate bond contains 31 kj (kilojoules) of energy.
Of course 1g on glucose contains many molecules