Optometry Admission Test (OAT) Practice 2026 - Free Optometry Admission Test Practice Questions and Study Guide

In the process of oxidative phosphorylation, NADH and FADH2 play crucial roles as coenzymes. They are both vital electron carriers that facilitate the transfer of electrons to the electron transport chain, which is located in the mitochondrial inner membrane in eukaryotic cells.

NADH is produced during several metabolic processes, including glycolysis, the citric acid cycle, and the conversion of pyruvate to acetyl-CoA. It carries high-energy electrons to the electron transport chain, which then uses this energy to pump protons across the mitochondrial membrane, creating an electrochemical gradient.

FADH2 is also generated during the citric acid cycle and serves a similar function in donating electrons to the electron transport chain, though it enters the chain at a different point than NADH, leading to less ATP production per molecule of FADH2 compared to NADH.

Both of these coenzymes are essential for the production of ATP via oxidative phosphorylation, as they provide the necessary electrons that drive the process of electron transport and ultimately ATP synthesis through the action of ATP synthase.

The other options involve molecules that are not directly part of the oxidative phosphorylation process. For example, ADP and ATP are involved in energy transfer but are not co