How many protons are transferred to the Pside by Complex I during its function?

Complex I, also known as NADH:ubiquinone oxidoreductase, is a crucial enzyme in the electron transport chain that plays an essential role in cellular respiration. During its function, Complex I catalyzes the transfer of electrons from NADH to ubiquinone (coenzyme Q), while simultaneously pumping protons from the mitochondrial matrix into the intermembrane space, which contributes to the proton motive force needed for ATP synthesis.

When NADH binds to Complex I, two electrons are extracted from NADH, leading to the reduction of ubiquinone to ubiquinol. As these electrons are transferred through the multiprotein complex, a total of four protons are translocated across the inner mitochondrial membrane into the intermembrane space. This translocation is crucial because it creates a gradient that will be utilized by ATP synthase to generate ATP.

The correct response indicates that four protons are indeed transferred to the Pside (intermembrane space) during the function of Complex I. This movement of protons is pivotal in the process of oxidative phosphorylation, highlighting the efficiency and importance of electron transport in energy production within the cell.