Energy_glycolysis_#reactions

It is not easy to break chemical  bonds. Each bond-breaking step may require a chemical reaction to accomplish the break. Such chemicals are often proteins (enzymes) that can break the bond. It can't be done all at once. That's a good thing too. If many bonds were broken all at once, so much bond energy might be released that it can't be captured all at once. Too much energy would be lost as heat.

Also, the chemicals that run the energy-extraction process have to be regenerated so that the process is self-sustaining. This also has to be done in small steps in a cyclic way, so that one chemical leads to another, and that to another, and so on, until the original compound is formed. These steps are accomplished by enzymes, each one  of which is unique for a given action. For example, one enzyme removes carbon dioxide from a compound  in the Krebs cycle and as a result a new compound is formed. The new compound is then acted on by another enzyme to produce yet another compound. Eventually, enzyme action on the last compound in the cycle regenerates the compound that started the cycle.