Atp production is more efficient in the presence of

In the presence of oxygen, one glucose molecule has the energy to make up to 38 ATP. The ATP production is determined by the following steps, (-2 ATP) glycolysis preparatory phase, (7-9 ATP) glycolysis pay-off phase, (5 ATP) oxidative decarboxylation of pyruvate and (20 ATP) Krebs cycle. One glucose which has 38 ATP hence was the summation of all the process mentioned that took place.  All these process take place under the cellular function of cellular respiration.
ATP usually releases energy by breaking down the weak phosphate cell present.  The energy released due to the breaking down of the phosphate cell is then utilized. The ATP is converted to ADP. Whenever a cell feels the necessity for energy it releases a phosphate to gather the energy. It is an automatic and ongoing process. The weak bond between the second and the third phosphate is always targeted for turning ATP to ADP. This is the reason ATP is considered the main energy currency for the cell. 

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