What role do hydrogen atoms play in the Krebs cycle?

In the Krebs cycle, hydrogen atoms primarily contribute as carriers of high-energy electrons that play a crucial role in cellular respiration. During the cycle, hydrogen atoms are transferred from substrates to electron carriers, specifically NAD+ and FAD, converting them to NADH and FADH2, respectively. These reduced coenzymes, NADH and FADH2, are then utilized in the electron transport chain, where they donate their electrons. This transfer of electrons leads to the generation of ATP, which is the energy currency of the cell.

The other options do not accurately reflect the function of hydrogen atoms in the Krebs cycle. For instance, hydrogen does not directly form glucose in this process; glucose formation occurs during photosynthesis and not in the Krebs cycle. Additionally, hydrogen atoms are not converted into oxygen, nor are they extraneous to cellular respiration; they are vital components that facilitate energy transfer through redox reactions.