Final answer:
In the electron transport chain, electron carriers pump H+ ions across the membrane against a gradient, creating an electrochemical gradient. This gradient is used to drive ATP synthesis. One example of an electron carrier is cytochrome c.
Step-by-step explanation:
In the electron transport chain, the free energy from the series of reactions is used to pump hydrogen ions (H+) across the membrane. This establishes an electrochemical gradient, with H+ ions being more concentrated on one side of the membrane. The movement of electrons down the chain fuels proton pumps, which alternate between electron carrier types, to pump H+ ions against the gradient.
One example of an electron carrier in the transport chain is cytochrome c, which shuttles electrons between the complexes. As electrons are transferred, H+ ions are pumped across the membrane. Other carriers, such as ubiquinone and flavin mononucleotide (FMN), also participate in this process.
The pumping of H+ ions creates a difference in proton concentration and electric potential across the membrane. This difference in gradients is known as the proton-motive force. It provides the energy for ATP synthase, an integral membrane protein, to allow the H+ ions to flow back into the matrix, driving the synthesis of ATP.