High-energy electrons from glycolysis and the Krebs cycle are ultimately transferred to NAD+ (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide).

Here's why:

* Glycolysis: During glycolysis, two molecules of NAD+ are reduced to NADH by gaining electrons.

* Krebs Cycle: The Krebs cycle generates even more NADH, as well as FADH2.

These electron carriers (NADH and FADH2) then transport the high-energy electrons to the electron transport chain, where they are used to generate ATP (adenosine triphosphate), the cell's primary energy currency.