Answer
Glycolysis is composed of two main steps:
1. Preparatory phase
2. Oxidative phase
In preparatory phase ATP is used for decomposition or conversion of glucose into two 3-carbon molecules i.e. glyceraldehyde 3-phosphate and dihydroxy acetone phosphate.
in oxidative phase, when these molecules convert into two pyruvate, ATP is produced.
Conclusion
Thus chemical energy is produced in oxidative phase of glycolysis.
