Final answer:
Electrons in the electron transport chain flow from ubiquinone with a redox potential of +30 mV to cytochrome c with a higher redox potential of +230 mV. Ubiquinone transfers electrons from complexes I and II to Complex III, while cytochrome c shuttles them from Complex III to Complex IV.
Step-by-step explanation:
In the electron transport chain, electrons flow from molecules with a lower redox potential to those with a higher redox potential. Since ubiquinone has a redox potential of +30 mV and cytochrome c has a redox potential of +230 mV, electrons will flow from ubiquinone to cytochrome c. This flow is a part of a series of redox reactions where each transfer of electrons is coupled to the transport of protons across the membrane, which ultimately drives the synthesis of ATP.
Ubiquinone, or coenzyme Q, receives electrons from complexes I and II and passes them to Complex III. Cytochrome c is a water-soluble protein that moves electrons from Complex III to Complex IV. The unique roles of ubiquinone and cytochrome c are crucial, as they ensure the step-wise flow of electrons, promoting the efficient production of ATP through oxidative phosphorylation.