Ask a Teacher

Search



HOW MANY KILO CALORIES OF ENERGY CAN BE OBTAINED FROM ONE MOLE OF GLUCOSE?.
When 1 mol (180 g) of glucose reacts with oxygen under standard conditions, 686 kcal of energy is released (DG0' = -686kcal/mol). If glucose is simply burned in air, all of this energy is released as heat. In the cell, however, this reaction is coupled to the synthesis of ATP from ADP in the following reaction:

C6H12O6 + 6O2 + 36Phosphate + 36ADP --> 6CO2 + 6H2O + 36ATP

In other words, the energy released when glucose reacts with oxygen is coupled with an endergonic reaction in order to produce ATP. However, only a fraction of the released energy goes into the high-energy bonds of ATP. Since the overall reaction is exergonic, some energy is lost as heat.
We can determine the efficiency of ATP production by comparing the energy in ATP created by the reaction to the energy released by the reaction:


where N is the number of ATP molecules formed and Ereact is the energy released as heat in the chemical reaction that is coupled with the reaction to form ATP. EATP is the energy in one high energy phophoanhydride bond in ATP, or the free energy when ATP reacts to form ADP and phosphate (ATP à ADP + phosphate).

Under standard conditions, Ereact = -686 kcal/mol and EATP = -7.3 kcal/mol. From the chemical reaction for the formation of ATP, we see that 36 molecules are formed.Therefore we calculate the efficiency as
In other words, only about 38.3% of the energy released from the reaction of glucose with oxygen is captured in ATP bonds.


comments powered by Disqus