Answer: As the electron transport carriers shuttle electrons, they actively pump hydrogen ions into the outer membrane compartment, setting up a concentration gradient called the proton motive force.
Step-by-step explanation:
The proton motive force is a form of potential energy created by the uneven distribution of hydrogen ions (protons) across a membrane. In cellular respiration, this membrane is usually the inner mitochondrial membrane or the thylakoid membrane in photosynthesis.
During electron transport in the inner mitochondrial membrane or thylakoid membrane, electrons are passed along a series of carriers, such as complex I, complex III, and complex IV in the electron transport chain. As electrons are transferred, hydrogen ions are actively pumped across the membrane, from the inner compartment to the outer compartment.
This active pumping of hydrogen ions creates a higher concentration of hydrogen ions in the outer membrane compartment compared to the inner membrane compartment. This concentration gradient is the proton motive force. The higher concentration of hydrogen ions in the outer compartment represents potential energy, which can be harnessed to do work, such as the synthesis of ATP (adenosine triphosphate) through ATP synthase.
ATP synthase is an enzyme that utilizes the flow of hydrogen ions back into the inner compartment, driven by the proton motive force, to generate ATP. As the hydrogen ions move down their concentration gradient through ATP synthase, the energy is captured and used to phosphorylate ADP (adenosine diphosphate), resulting in the production of ATP.
In summary, the concentration gradient created by the active pumping of hydrogen ions into the outer membrane compartment during electron transport is called the proton motive force. This gradient represents potential energy and is utilized by ATP synthase to produce ATP.