How many protons are pumped out of complex I in the oxidative phosphorylation and electron transport chain?
The correct answer and explanation is:
The correct answer is 4 protons.
In oxidative phosphorylation and the electron transport chain, complex I (also known as NADH dehydrogenase) plays a crucial role in the transfer of electrons and the creation of a proton gradient. Complex I receives electrons from NADH, which is oxidized to NAD+ in the process. These electrons are then passed through a series of protein complexes within complex I and ultimately transferred to ubiquinone, which becomes ubiquinol (QH2).
As electrons move through complex I, the energy released is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space, creating a proton gradient. This gradient is essential for driving the production of ATP through ATP synthase, a process known as chemiosmosis.
The number of protons pumped out by complex I is 4 per pair of electrons that pass through. This is significant because the proton gradient generated by these protons is used by ATP synthase to produce ATP. The proton gradient establishes an electrochemical potential, and as protons flow back through ATP synthase, the energy is harnessed to convert ADP to ATP.
Understanding the exact number of protons pumped by each complex is crucial for appreciating the efficiency of cellular respiration. Complex I contributes to the total proton gradient that powers ATP synthesis, but it is also important to note that other complexes, such as complex III and complex IV, also pump protons as part of the overall process.
In summary, complex I pumps 4 protons per pair of electrons during the electron transport chain, helping to establish the proton gradient necessary for ATP production in oxidative phosphorylation.