The main electron carriers in the Krebs cycle (also known as the citric acid cycle) are:

* NAD+ (Nicotinamide adenine dinucleotide): It accepts two electrons and one proton (H+) to become NADH.

* FAD (Flavin adenine dinucleotide): It accepts two electrons and two protons to become FADH2.

Both NADH and FADH2 are important because they carry high-energy electrons to the electron transport chain, where they are used to generate ATP (adenosine triphosphate), the primary energy currency of the cell.