Answer:
Energetic electrons that provide the energy for the production of most of a cell"s ATP are carried to the electron transport system by reduced co enzymes such as NADH,FADH2.
Step-by-step explanation:
During glycolysis and TCA cycle maximum redox reaction utilizes either NAD+ or FAD .NAD+ and FAD are used as co enzymes which get reduced to NADH and FADH2 during various re dox reactions of aerobic respiration.
But this reduced co enzymes should be converted to active form and to do this the reduced co enzymes such as NADH and FADH2 enter into electron transport chain to donate electrons thus converting them into their active form.